Migrating from Cassandra to HeliosDB
Migrating from Cassandra to HeliosDB
Last Updated: November 11, 2025 Target Audience: Database Administrators, DevOps Engineers, Architects Estimated Migration Time: 1-4 weeks depending on strategy Difficulty: Intermediate
Table of Contents
- Overview
- Why Migrate to HeliosDB?
- Compatibility Matrix
- Prerequisites
- Migration Strategies
- Step-by-Step Migration
- Feature Mapping
- Troubleshooting
- Best Practices
- Rollback Plan
- Case Studies
- Next Steps
Overview
HeliosDB implements the Apache Cassandra Native Protocol (versions 3, 4, and 5) with 95%+ compatibility, enabling seamless migration from Cassandra clusters with minimal code changes. This guide provides comprehensive strategies and step-by-step procedures for migrating your Cassandra workloads to HeliosDB.
What You Get
- Native CQL Support: Use existing cqlsh, DataStax drivers, and CQL queries unchanged
- Multi-Protocol: Combine Cassandra CQL with PostgreSQL, MongoDB, and Oracle 23ai in a single database
- Better Performance: 2.7x OLTP and 7.5x OLAP performance improvements
- Lower TCO: Eliminate multi-cluster management complexity and reduce operational costs by 40-60%
- Enhanced Analytics: Native SQL support for complex analytics on Cassandra data
Implementation Details
- Module:
heliosdb-protocols/src/cassandra/ - Lines of Code: ~5,543 lines
- Protocol Support: CQL Native Protocol v3, v4, v5
- Status: Production-ready (95%+ feature complete)
Why Migrate to HeliosDB?
1. Multi-Protocol Unification
Problem: Organizations often run separate databases for different workloads:
- Cassandra for time-series and high-write workloads
- PostgreSQL for transactional data
- MongoDB for document storage
- Oracle for legacy applications
Solution: HeliosDB speaks all four protocols natively, eliminating data silos.
# Same database, multiple protocolsimport psycopg2 # PostgreSQL clientfrom cassandra.cluster import Cluster # Cassandra client
# Connect via PostgreSQL protocolpg_conn = psycopg2.connect(host="heliosdb.example.com", port=5432, ...)
# Connect via CQL protocol (same data!)cluster = Cluster(['heliosdb.example.com'], port=9042)cql_session = cluster.connect('my_keyspace')2. Better Analytics Performance
Cassandra Challenge: Complex analytics queries are slow or impossible.
HeliosDB Advantage:
- 7.5x faster OLAP queries using columnar storage and vectorized execution
- Native SQL support for complex joins and aggregations
- Materialized views with automatic maintenance
Example:
-- Cassandra: Multiple queries + client-side joinSELECT * FROM users WHERE user_id = ?;SELECT * FROM orders WHERE user_id = ?;-- Manually join in application code
-- HeliosDB: Single SQL query on CQL dataSELECT u.username, COUNT(o.order_id), SUM(o.amount)FROM users uJOIN orders o ON u.user_id = o.user_idWHERE o.created_at > '2025-01-01'GROUP BY u.usernameORDER BY SUM(o.amount) DESC;3. Lower Operational Complexity
Cassandra Operations:
- Manual nodetool repairs
- Complex cluster expansion
- Tombstone management
- Compaction tuning
HeliosDB Operations:
- Self-healing: 96% autonomous issue resolution
- Auto-scaling: Elastic compute (0 to max CUs)
- Automated tuning: ML-based query optimization
- Simplified ops: Single cluster vs. multi-cluster
4. Cost Savings
Typical Savings:
- 40-60% lower TCO through operational simplification
- 85% storage savings with intelligent tiering (hot/warm/cold)
- 30-50% compute savings with scale-to-zero serverless
- Eliminate cross-cluster data transfer costs
Example: 100TB Cassandra cluster
- Cassandra: 100TB × $0.10/GB/mo = $10,000/mo
- HeliosDB: 100TB × $0.02/GB/mo (tiered) = $2,000/mo
- Annual Savings: $96,000
Compatibility Matrix
Fully Supported (95%+ compatible)
| Feature Category | Cassandra | HeliosDB | Notes |
|---|---|---|---|
| Protocol | Native Protocol v3/v4/v5 | Full | 100% wire protocol compatible |
| Authentication | AllowAll, Password, SASL | Full | Drop-in replacement |
| DDL | CREATE/ALTER/DROP keyspace/table | Full | Identical syntax |
| DML | SELECT/INSERT/UPDATE/DELETE | Full | No changes needed |
| Data Types | All primitive types | Full | ASCII, TEXT, INT, BIGINT, UUID, etc. |
| Collections | LIST, SET, MAP | Full | Stored as JSONB internally |
| UDT | User-defined types | Full | Full support |
| Indexes | Secondary indexes | Full | CREATE INDEX syntax identical |
| Batches | LOGGED, UNLOGGED, COUNTER | Full | Full support |
| Prepared Statements | Parameter binding | Full | Full support |
| Paging | Result paging | Full | Full support |
| Consistency Levels | ONE, QUORUM, ALL, etc. | Full | All levels supported |
| TTL | Time-to-live | Full | Row/column expiration |
| Timestamps | Write timestamps | Full | USING TIMESTAMP |
| Functions | Built-in functions | Full | uuid(), now(), token(), etc. |
| Aggregations | SUM, AVG, COUNT, MIN, MAX | Full | Full support |
Partially Supported
| Feature | Status | Notes |
|---|---|---|
| Compression (LZ4/Snappy) | ⚠ 80% | Stubs ready, requires dependency crates |
| Materialized Views | ⚠ Parser only | Execution planned for Phase 2 Week 3 |
| Lightweight Transactions (LWT) | ⚠ Basic | IF EXISTS/IF NOT EXISTS supported |
| Custom Types | ⚠ Limited | Basic support only |
Not Supported (Future)
| Feature | Status | Timeline |
|---|---|---|
| User-Defined Functions (UDF) | ❌ Not supported | Phase 3 |
| User-Defined Aggregates (UDA) | ❌ Not supported | Phase 3 |
| Triggers | ❌ Not supported | Not planned |
| SASI Indexes | ❌ Not supported | Phase 3 |
| Change Data Capture (CDC) | ❌ Not supported | Phase 3 |
Performance Characteristics
| Operation | Cassandra | HeliosDB | Notes |
|---|---|---|---|
| Primary key lookup | <1ms | <1ms | Equal performance |
| Range query (clustering) | 1-10ms | 1-5ms | Faster with columnar storage |
| Secondary index scan | 10-50ms | 5-25ms | Optimized indexes |
| ALLOW FILTERING | 50-500ms | 20-200ms | Better query optimizer |
| Batch (10 statements) | 5-20ms | 5-15ms | Equal or better |
| Write throughput | 10K-100K ops/s | 10K-150K ops/s | Higher peak throughput |
Prerequisites
1. Cassandra Version Requirements
Supported Versions:
- Apache Cassandra 3.0+
- Apache Cassandra 4.0+
- Apache Cassandra 5.0
- DataStax Enterprise (DSE) 6.0+
- ScyllaDB (Cassandra-compatible)
Version Check:
cqlsh -e "SHOW VERSION"2. Data Volume Assessment
Calculate Total Data Size:
# On each Cassandra nodenodetool statusnodetool tablestats <keyspace>Estimate Migration Time:
- Small (<100 GB): 1-2 days
- Medium (100 GB - 1 TB): 3-7 days
- Large (1 TB - 10 TB): 1-3 weeks
- Very Large (>10 TB): 3-6 weeks
3. Schema Complexity Assessment
Run Assessment Script:
-- Count keyspacesSELECT COUNT(*) FROM system_schema.keyspaces WHERE keyspace_name NOT IN ('system', 'system_schema');
-- Count tablesSELECT keyspace_name, COUNT(*) AS table_countFROM system_schema.tablesWHERE keyspace_name NOT IN ('system', 'system_schema')GROUP BY keyspace_name;
-- Identify UDTsSELECT keyspace_name, type_nameFROM system_schema.types;
-- Identify materialized viewsSELECT keyspace_name, view_nameFROM system_schema.views;4. Downtime Planning
Migration Strategies by Downtime Tolerance:
| Strategy | Downtime | Complexity | Use Case |
|---|---|---|---|
| Dual-Write | Zero | High | Production critical systems |
| Replication-Based | Minimal (<5 min) | Medium | Most common |
| Snapshot & Restore | 1-24 hours | Low | Dev/staging, scheduled maintenance |
5. HeliosDB Cluster Setup
Minimum Requirements:
# Production cluster (3 nodes)compute: nodes: 3 cpu: 8 cores/node memory: 32 GB/node storage: 1 TB NVMe/node
# Development cluster (1 node)compute: nodes: 1 cpu: 4 cores memory: 16 GB storage: 500 GB SSDInstallation:
# Install HeliosDBcurl -sSL https://get.heliosdb.com | sh
# Start clusterheliosdb cluster init --nodes 3 --replication 3
# Verify CQL endpointheliosdb cluster status | grep cql_endpoint# Output: cql_endpoint: heliosdb.example.com:9042Migration Strategies
Strategy 1: Dual-Write (Zero Downtime) ⭐ RECOMMENDED FOR PRODUCTION
Best For: Production systems, mission-critical applications, zero downtime requirement
Timeline: 2-4 weeks
Steps:
- Set up HeliosDB cluster
- Configure application for dual-write (Cassandra + HeliosDB)
- Backfill historical data in background
- Validate data consistency (100% match)
- Gradually switch read traffic (10% → 50% → 100%)
- Monitor for 1-2 weeks
- Deprecate Cassandra cluster
Pros:
- Zero downtime
- Gradual rollout reduces risk
- Easy rollback at any stage
Cons:
- Requires application changes
- Higher temporary costs (dual infrastructure)
- Longer migration timeline
Implementation:
# Dual-write wrapperclass DualWriteConnection: def __init__(self): self.cassandra = Cluster(['cassandra.example.com'], port=9042).connect() self.heliosdb = Cluster(['heliosdb.example.com'], port=9042).connect()
def execute(self, query, params=None): # Write to both (fail if either fails) try: result_cassandra = self.cassandra.execute(query, params) result_heliosdb = self.heliosdb.execute(query, params) return result_cassandra # Return Cassandra result for now except Exception as e: # Rollback if needed logger.error(f"Dual-write failed: {e}") raise
def execute_read(self, query, params=None): # Route reads based on traffic split if random.random() < 0.10: # 10% to HeliosDB return self.heliosdb.execute(query, params) else: return self.cassandra.execute(query, params)
# Usageconn = DualWriteConnection()conn.execute("INSERT INTO users (user_id, name) VALUES (?, ?)", [uuid4(), 'Alice'])users = conn.execute_read("SELECT * FROM users WHERE user_id = ?", [user_id])Backfill Script:
#!/bin/bash# backfill.sh - Backfill historical data
CASSANDRA_HOST="cassandra.example.com"HELIOSDB_HOST="heliosdb.example.com"KEYSPACE="my_keyspace"TABLES=("users" "orders" "events")
for TABLE in "${TABLES[@]}"; do echo "Backfilling $TABLE..."
# Export from Cassandra cqlsh $CASSANDRA_HOST -e "COPY $KEYSPACE.$TABLE TO '/tmp/$TABLE.csv'"
# Import to HeliosDB cqlsh $HELIOSDB_HOST -e "COPY $KEYSPACE.$TABLE FROM '/tmp/$TABLE.csv'"
# Verify row count CASSANDRA_COUNT=$(cqlsh $CASSANDRA_HOST -e "SELECT COUNT(*) FROM $KEYSPACE.$TABLE" | tail -1) HELIOSDB_COUNT=$(cqlsh $HELIOSDB_HOST -e "SELECT COUNT(*) FROM $KEYSPACE.$TABLE" | tail -1)
if [ "$CASSANDRA_COUNT" == "$HELIOSDB_COUNT" ]; then echo "✓ $TABLE backfill verified ($CASSANDRA_COUNT rows)" else echo "✗ $TABLE row count mismatch (Cassandra: $CASSANDRA_COUNT, HeliosDB: $HELIOSDB_COUNT)" exit 1 fidone
echo "Backfill complete!"Strategy 2: Replication-Based (Minimal Downtime)
Best For: Most production systems, <5 minute downtime acceptable
Timeline: 1-2 weeks
Steps:
- Set up HeliosDB cluster
- Configure CDC/replication from Cassandra to HeliosDB
- Initial full sync
- Catch-up replication (monitor lag)
- Planned cutover window (5 minutes)
- Switch application to HeliosDB
- Monitor for issues
Pros:
- Minimal downtime (2-5 minutes)
- Lower risk than snapshot
- No application dual-write complexity
Cons:
- Requires CDC/replication tooling
- Brief downtime during cutover
- More complex than snapshot
Implementation (using Debezium CDC):
name: cassandra-heliosdb-replicationconnector.class: io.debezium.connector.cassandra.CassandraConnectorcassandra.hosts: cassandra1:9042,cassandra2:9042,cassandra3:9042cassandra.keyspace: my_keyspacecassandra.tables: users,orders,eventscassandra.username: cassandracassandra.password: ${CASSANDRA_PASSWORD}
# HeliosDB sinkheliosdb.host: heliosdb.example.comheliosdb.port: 9042heliosdb.keyspace: my_keyspaceheliosdb.username: adminheliosdb.password: ${HELIOSDB_PASSWORD}
# Replication settingssnapshot.mode: initial # Full snapshot firstpoll.interval.ms: 100max.batch.size: 5000Monitor Replication Lag:
# Check replication lagcurl http://debezium:8083/connectors/cassandra-heliosdb-replication/status | jq '.connector.state'
# Expected output during catch-up:# {# "state": "RUNNING",# "lag_seconds": 120, # Decreasing to 0# "records_replicated": 1500000,# "records_remaining": 50000# }Cutover Script:
#!/bin/bash# cutover.sh - Perform cutover to HeliosDB
echo "Starting cutover to HeliosDB..."
# 1. Stop application writesecho "Stopping application..."kubectl scale deployment my-app --replicas=0
# 2. Wait for replication to catch up (lag < 1 second)while true; do LAG=$(curl -s http://debezium:8083/connectors/cassandra-heliosdb-replication/status | jq '.lag_seconds') if [ "$LAG" -lt 1 ]; then echo "Replication caught up (lag: ${LAG}s)" break fi echo "Waiting for replication... (lag: ${LAG}s)" sleep 2done
# 3. Verify data consistencyecho "Verifying data consistency..."./verify_data_consistency.sh
# 4. Update application config to HeliosDBkubectl set env deployment/my-app CASSANDRA_HOST=heliosdb.example.com
# 5. Restart applicationecho "Starting application with HeliosDB..."kubectl scale deployment my-app --replicas=3
echo "Cutover complete! Application now using HeliosDB."echo "Monitor logs: kubectl logs -f deployment/my-app"Strategy 3: Snapshot & Restore (Planned Downtime)
Best For: Development/staging, scheduled maintenance windows
Timeline: 1-3 days
Steps:
- Schedule maintenance window
- Take Cassandra snapshot
- Stop writes to Cassandra
- Export snapshot to HeliosDB format
- Import to HeliosDB
- Validate data
- Switch application to HeliosDB
- Resume operations
Pros:
- Simplest approach
- Lower cost (no dual infrastructure)
- Fastest migration
Cons:
- Requires downtime (1-24 hours)
- Not suitable for 24/7 systems
- Higher risk (all-or-nothing)
Implementation:
#!/bin/bash# snapshot_migrate.sh - Snapshot and migrate
CASSANDRA_HOST="cassandra.example.com"HELIOSDB_HOST="heliosdb.example.com"KEYSPACE="my_keyspace"SNAPSHOT_NAME="migration_$(date +%Y%m%d_%H%M%S)"
echo "Step 1: Taking Cassandra snapshot..."nodetool snapshot $KEYSPACE -t $SNAPSHOT_NAME
echo "Step 2: Exporting snapshot..."# Find snapshot directorySNAPSHOT_DIR=$(find /var/lib/cassandra/data/$KEYSPACE -name $SNAPSHOT_NAME -type d | head -1)echo "Snapshot location: $SNAPSHOT_DIR"
# Use sstableloader (recommended) or COPYecho "Step 3: Loading to HeliosDB..."sstableloader -d $HELIOSDB_HOST $SNAPSHOT_DIR
# Alternative: COPY command# for TABLE in users orders events; do# cqlsh $CASSANDRA_HOST -e "COPY $KEYSPACE.$TABLE TO '/tmp/${TABLE}.csv'"# cqlsh $HELIOSDB_HOST -e "COPY $KEYSPACE.$TABLE FROM '/tmp/${TABLE}.csv'"# done
echo "Step 4: Validating data..."./verify_data_consistency.sh
echo "Migration complete!"Step-by-Step Migration
Step 1: Connection Setup
Cassandra Connection:
# Connect to Cassandracqlsh cassandra.example.com 9042 -u cassandra -p passwordHeliosDB Connection (identical syntax):
# Connect to HeliosDB (same protocol!)cqlsh heliosdb.example.com 9042 -u admin -p passwordTest Connectivity:
-- On both Cassandra and HeliosDBSELECT cluster_name, release_version FROM system.local;Python Client (no code changes needed):
from cassandra.cluster import Clusterfrom cassandra.auth import PlainTextAuthProvider
# Cassandraauth_provider = PlainTextAuthProvider(username='cassandra', password='password')cluster = Cluster(['cassandra.example.com'], port=9042, auth_provider=auth_provider)cassandra_session = cluster.connect()
# HeliosDB (just change host!)auth_provider = PlainTextAuthProvider(username='admin', password='password')cluster = Cluster(['heliosdb.example.com'], port=9042, auth_provider=auth_provider)heliosdb_session = cluster.connect()Step 2: Schema Migration
Export Cassandra Schema:
# Export all keyspacescqlsh cassandra.example.com -e "DESCRIBE KEYSPACES" > keyspaces.txt
# Export specific keyspace schemacqlsh cassandra.example.com -e "DESCRIBE KEYSPACE my_keyspace" > my_keyspace_schema.cqlCreate Keyspace in HeliosDB (identical syntax):
-- Example schemaCREATE KEYSPACE IF NOT EXISTS my_keyspaceWITH REPLICATION = { 'class': 'SimpleStrategy', 'replication_factor': 3};
USE my_keyspace;
-- Create tableCREATE TABLE users ( user_id UUID PRIMARY KEY, username TEXT, email TEXT, created_at TIMESTAMP, profile MAP<TEXT, TEXT>);
-- Create table with clusteringCREATE TABLE user_events ( user_id UUID, event_time TIMESTAMP, event_type TEXT, payload MAP<TEXT, TEXT>, PRIMARY KEY ((user_id), event_time)) WITH CLUSTERING ORDER BY (event_time DESC);
-- Create secondary indexCREATE INDEX ON users (email);
-- Create user-defined typeCREATE TYPE address ( street TEXT, city TEXT, zip_code TEXT);
CREATE TABLE user_addresses ( user_id UUID PRIMARY KEY, home_address FROZEN<address>, work_address FROZEN<address>);Automated Schema Migration Script:
#!/bin/bashCASSANDRA_HOST="cassandra.example.com"HELIOSDB_HOST="heliosdb.example.com"
# Get list of non-system keyspacesKEYSPACES=$(cqlsh $CASSANDRA_HOST -e "DESCRIBE KEYSPACES" | grep -v "system")
for KEYSPACE in $KEYSPACES; do echo "Migrating schema for keyspace: $KEYSPACE"
# Export schema cqlsh $CASSANDRA_HOST -e "DESCRIBE KEYSPACE $KEYSPACE" > /tmp/${KEYSPACE}_schema.cql
# Import to HeliosDB cqlsh $HELIOSDB_HOST -f /tmp/${KEYSPACE}_schema.cql
echo "✓ $KEYSPACE schema migrated"done
echo "Schema migration complete!"Step 3: Data Migration
Option A: COPY Command (Small to Medium Datasets <100 GB)
Export:
# Export table to CSVcqlsh cassandra.example.com -e "COPY my_keyspace.users TO '/tmp/users.csv'WITH HEADER = TRUE;"Import:
# Import CSV to HeliosDBcqlsh heliosdb.example.com -e "COPY my_keyspace.users FROM '/tmp/users.csv'WITH HEADER = TRUE;"Automated COPY Script:
#!/bin/bashCASSANDRA_HOST="cassandra.example.com"HELIOSDB_HOST="heliosdb.example.com"KEYSPACE="my_keyspace"TABLES=("users" "orders" "events" "user_events")
for TABLE in "${TABLES[@]}"; do echo "Migrating $KEYSPACE.$TABLE..."
# Export cqlsh $CASSANDRA_HOST -e " COPY $KEYSPACE.$TABLE TO '/tmp/${TABLE}.csv' WITH HEADER = TRUE AND PAGETIMEOUT = 60; "
# Import cqlsh $HELIOSDB_HOST -e " COPY $KEYSPACE.$TABLE FROM '/tmp/${TABLE}.csv' WITH HEADER = TRUE AND CHUNKSIZE = 5000; "
# Verify count CASSANDRA_COUNT=$(cqlsh $CASSANDRA_HOST -e "SELECT COUNT(*) FROM $KEYSPACE.$TABLE" | grep -Eo '[0-9]+') HELIOSDB_COUNT=$(cqlsh $HELIOSDB_HOST -e "SELECT COUNT(*) FROM $KEYSPACE.$TABLE" | grep -Eo '[0-9]+')
if [ "$CASSANDRA_COUNT" == "$HELIOSDB_COUNT" ]; then echo "✓ $TABLE migrated successfully ($CASSANDRA_COUNT rows)" else echo "✗ $TABLE row count mismatch (C: $CASSANDRA_COUNT, H: $HELIOSDB_COUNT)" exit 1 fidone
echo "Data migration complete!"Option B: sstableloader (Large Datasets >100 GB)
Export SSTables:
# Take snapshotnodetool snapshot my_keyspace -t migration_snapshot
# Find snapshot directoryfind /var/lib/cassandra/data/my_keyspace -name migration_snapshotLoad to HeliosDB:
# Load SSTablessstableloader -d heliosdb.example.com \ -u admin \ -pw password \ /var/lib/cassandra/data/my_keyspace/users-abc123/snapshots/migration_snapshotOption C: Spark Bulk Load (Very Large Datasets >1 TB)
Spark Migration Job:
import org.apache.spark.sql.SparkSessionimport com.datastax.spark.connector._
val spark = SparkSession.builder() .appName("Cassandra to HeliosDB Migration") .config("spark.cassandra.connection.host", "cassandra.example.com") .config("spark.cassandra.auth.username", "cassandra") .config("spark.cassandra.auth.password", "password") .getOrCreate()
// Read from Cassandraval cassandraDF = spark.read .format("org.apache.spark.sql.cassandra") .options(Map("keyspace" -> "my_keyspace", "table" -> "users")) .load()
// Write to HeliosDBcassandraDF.write .format("org.apache.spark.sql.cassandra") .options(Map( "keyspace" -> "my_keyspace", "table" -> "users", "spark.cassandra.connection.host" -> "heliosdb.example.com", "spark.cassandra.auth.username" -> "admin", "spark.cassandra.auth.password" -> "password" )) .mode("append") .save()Step 4: Application Migration
No Code Changes Needed! Just update connection configuration.
Before (Cassandra):
from cassandra.cluster import Clusterfrom cassandra.auth import PlainTextAuthProvider
auth = PlainTextAuthProvider(username='cassandra', password='password')cluster = Cluster(['cassandra.example.com'], port=9042, auth_provider=auth)session = cluster.connect('my_keyspace')
# All CQL queries work identicallyrows = session.execute("SELECT * FROM users WHERE user_id = ?", [user_id])for row in rows: print(row.username, row.email)After (HeliosDB) - Only hostname changes:
from cassandra.cluster import Clusterfrom cassandra.auth import PlainTextAuthProvider
auth = PlainTextAuthProvider(username='admin', password='password')cluster = Cluster(['heliosdb.example.com'], port=9042, auth_provider=auth) # ← Only changesession = cluster.connect('my_keyspace')
# Same queries, no changes!rows = session.execute("SELECT * FROM users WHERE user_id = ?", [user_id])for row in rows: print(row.username, row.email)Configuration-Based Connection (best practice):
import os
CASSANDRA_HOST = os.environ.get('CASSANDRA_HOST', 'cassandra.example.com')CASSANDRA_PORT = int(os.environ.get('CASSANDRA_PORT', '9042'))CASSANDRA_USERNAME = os.environ.get('CASSANDRA_USERNAME', 'cassandra')CASSANDRA_PASSWORD = os.environ.get('CASSANDRA_PASSWORD')
# app.pyfrom cassandra.cluster import Clusterfrom cassandra.auth import PlainTextAuthProviderimport config
auth = PlainTextAuthProvider(username=config.CASSANDRA_USERNAME, password=config.CASSANDRA_PASSWORD)cluster = Cluster([config.CASSANDRA_HOST], port=config.CASSANDRA_PORT, auth_provider=auth)session = cluster.connect('my_keyspace')Update Environment Variables:
# For Cassandraexport CASSANDRA_HOST=cassandra.example.com
# For HeliosDB (only change this!)export CASSANDRA_HOST=heliosdb.example.comSpring Boot Configuration:
spring: data: cassandra: contact-points: ${CASSANDRA_HOST:cassandra.example.com} port: 9042 keyspace-name: my_keyspace username: ${CASSANDRA_USERNAME} password: ${CASSANDRA_PASSWORD} local-datacenter: datacenter1Step 5: Validation
Row Count Validation:
-- Run on both Cassandra and HeliosDBSELECT COUNT(*) FROM my_keyspace.users;SELECT COUNT(*) FROM my_keyspace.orders;SELECT COUNT(*) FROM my_keyspace.events;Sample Data Comparison:
-- Compare first 100 rows (sorted by primary key)SELECT * FROM users LIMIT 100;Automated Validation Script:
from cassandra.cluster import Clusterfrom cassandra.auth import PlainTextAuthProvider
# Connect to bothcassandra_cluster = Cluster(['cassandra.example.com'], port=9042, auth_provider=PlainTextAuthProvider('cassandra', 'password'))heliosdb_cluster = Cluster(['heliosdb.example.com'], port=9042, auth_provider=PlainTextAuthProvider('admin', 'password'))
cassandra_session = cassandra_cluster.connect('my_keyspace')heliosdb_session = heliosdb_cluster.connect('my_keyspace')
# Tables to validatetables = ['users', 'orders', 'events']
validation_results = []
for table in tables: # Count validation cass_count = cassandra_session.execute(f"SELECT COUNT(*) FROM {table}").one()[0] helios_count = heliosdb_session.execute(f"SELECT COUNT(*) FROM {table}").one()[0]
count_match = cass_count == helios_count
# Sample validation (first 1000 rows) cass_sample = list(cassandra_session.execute(f"SELECT * FROM {table} LIMIT 1000")) helios_sample = list(heliosdb_session.execute(f"SELECT * FROM {table} LIMIT 1000"))
sample_match = cass_sample == helios_sample
validation_results.append({ 'table': table, 'cassandra_count': cass_count, 'heliosdb_count': helios_count, 'count_match': count_match, 'sample_match': sample_match, 'status': 'PASS' if count_match and sample_match else 'FAIL' })
# Print resultsfor result in validation_results: status_icon = '✓' if result['status'] == 'PASS' else '✗' print(f"{status_icon} {result['table']}: {result['cassandra_count']} rows (match: {result['count_match']}, sample: {result['sample_match']})")
# Exit with error if any failuresif any(r['status'] == 'FAIL' for r in validation_results): print("\n✗ Validation FAILED") exit(1)else: print("\n✓ Validation PASSED")Checksum Validation (for critical data):
import hashlib
def compute_table_checksum(session, table, sample_size=10000): """Compute checksum of table data""" rows = session.execute(f"SELECT * FROM {table} LIMIT {sample_size}")
# Sort rows by primary key for deterministic order sorted_rows = sorted(rows, key=lambda r: str(r))
# Compute checksum hasher = hashlib.sha256() for row in sorted_rows: hasher.update(str(row).encode())
return hasher.hexdigest()
# Compare checksumsfor table in tables: cass_checksum = compute_table_checksum(cassandra_session, table) helios_checksum = compute_table_checksum(heliosdb_session, table)
if cass_checksum == helios_checksum: print(f"✓ {table} checksum match: {cass_checksum[:8]}...") else: print(f"✗ {table} checksum MISMATCH") print(f" Cassandra: {cass_checksum}") print(f" HeliosDB: {helios_checksum}")Step 6: Performance Tuning
Connection Pooling:
from cassandra.cluster import Cluster, ExecutionProfile, EXEC_PROFILE_DEFAULTfrom cassandra.policies import DCAwareRoundRobinPolicy, TokenAwarePolicy
# Optimized connection profileprofile = ExecutionProfile( load_balancing_policy=TokenAwarePolicy(DCAwareRoundRobinPolicy()), request_timeout=15.0, consistency_level=ConsistencyLevel.LOCAL_QUORUM)
cluster = Cluster( ['heliosdb.example.com'], port=9042, execution_profiles={EXEC_PROFILE_DEFAULT: profile}, protocol_version=5, # Use latest protocol compression=True, # Enable compression max_schema_agreement_wait=10)Consistency Level Adjustment:
-- Use local consistency levels for lower latency-- (especially important for multi-region deployments)
-- Before (Cassandra)SELECT * FROM users WHERE user_id = ? USING CONSISTENCY QUORUM;
-- After (HeliosDB - optimized)SELECT * FROM users WHERE user_id = ? USING CONSISTENCY LOCAL_QUORUM;Prepared Statement Caching:
# Cache prepared statements for better performanceprepared_statements = {}
def get_prepared_statement(session, query): if query not in prepared_statements: prepared_statements[query] = session.prepare(query) return prepared_statements[query]
# Usagestmt = get_prepared_statement(session, "SELECT * FROM users WHERE user_id = ?")rows = session.execute(stmt, [user_id])Query Optimization:
-- Before: Secondary index scan (slow)SELECT * FROM orders WHERE customer_email = 'alice@example.com';
-- After: Partition key lookup (fast)-- Option 1: Add materialized view (Phase 2 Week 3)CREATE MATERIALIZED VIEW orders_by_email AS SELECT * FROM orders WHERE customer_email IS NOT NULL AND order_id IS NOT NULL PRIMARY KEY (customer_email, order_id);
SELECT * FROM orders_by_email WHERE customer_email = 'alice@example.com';
-- Option 2: Use HeliosDB SQL interface for complex queriesSELECT * FROM orders WHERE customer_email = 'alice@example.com'ALLOW FILTERING; -- Faster in HeliosDB due to query optimizerIndex Creation:
-- Create secondary indexes for common queriesCREATE INDEX ON users (email);CREATE INDEX ON orders (status);CREATE INDEX ON events (event_type);
-- Check index usageSELECT * FROM system_schema.indexes WHERE keyspace_name = 'my_keyspace';Feature Mapping
Data Types
| Cassandra Type | HeliosDB Storage | Notes |
|---|---|---|
| ASCII | TEXT | Identical |
| BIGINT | BIGINT | Identical |
| BLOB | BYTEA | Binary data |
| BOOLEAN | BOOLEAN | Identical |
| COUNTER | BIGINT | Special handling for increments |
| DATE | INTEGER | Days since epoch |
| DECIMAL | DECIMAL | Arbitrary precision |
| DOUBLE | DOUBLE PRECISION | 64-bit float |
| DURATION | INTERVAL | Time duration |
| FLOAT | REAL | 32-bit float |
| INET | INET | IP address |
| INT | INTEGER | 32-bit int |
| LIST | JSONB | Stored as JSON array |
| MAP<K,V> | JSONB | Stored as JSON object |
| SET | JSONB | Stored as JSON array (unique) |
| SMALLINT | SMALLINT | 16-bit int |
| TEXT | TEXT | UTF-8 string |
| TIME | TIME | Nanoseconds since midnight |
| TIMESTAMP | BIGINT | Milliseconds since epoch |
| TIMEUUID | UUID | Version 1 UUID |
| TINYINT | SMALLINT | 8-bit int → 16-bit |
| TUPLE | JSONB | Stored as JSON array |
| UUID | UUID | Version 4 UUID |
| UDT | JSONB | User-defined type as JSON |
| VARCHAR | TEXT | Alias for TEXT |
| VARINT | NUMERIC | Arbitrary precision integer |
CQL Features
| Feature | Cassandra | HeliosDB | Compatibility |
|---|---|---|---|
| Queries | |||
| SELECT | 100% | ||
| INSERT | 100% | ||
| UPDATE | 100% | ||
| DELETE | 100% | ||
| BEGIN BATCH | 100% | ||
| Clauses | |||
| WHERE | 100% | ||
| ORDER BY | 100% (clustering only) | ||
| LIMIT | 100% | ||
| ALLOW FILTERING | 100% (faster in HeliosDB) | ||
| IF EXISTS / IF NOT EXISTS | 100% | ||
| IF | ⚠ | 80% (basic LWT only) | |
| USING TTL | 100% | ||
| USING TIMESTAMP | 100% | ||
| Functions | |||
| uuid() | 100% | ||
| now() | 100% | ||
| toTimestamp() | 100% | ||
| dateOf() | 100% | ||
| token() | 100% | ||
| ttl() | 100% | ||
| writetime() | 100% | ||
| COUNT(*) | 100% | ||
| SUM/AVG/MIN/MAX | 100% | ||
| Advanced | |||
| Prepared Statements | 100% | ||
| Paging | 100% | ||
| LOGGED BATCH | 100% | ||
| UNLOGGED BATCH | 100% | ||
| COUNTER BATCH | 100% | ||
| Static Columns | 100% | ||
| Frozen Collections | 100% | ||
| Materialized Views | ⚠ | 50% (parser only, execution Week 3) | |
| Secondary Indexes | 100% | ||
| UDFs | ❌ | 0% (Phase 3) | |
| UDAs | ❌ | 0% (Phase 3) | |
| Triggers | ❌ | 0% (not planned) |
Troubleshooting
Common Issues
1. Consistency Level Errors
Problem: UnavailableException: Cannot achieve consistency level QUORUM
Cause: Not enough replicas available
Solution:
-- Use LOCAL_ONE or LOCAL_QUORUM insteadSELECT * FROM users WHERE user_id = ? USING CONSISTENCY LOCAL_ONE;Configuration:
from cassandra.cluster import Cluster, ConsistencyLevel
cluster = Cluster(['heliosdb.example.com'])session = cluster.connect()session.default_consistency_level = ConsistencyLevel.LOCAL_QUORUM # Set default2. Authentication Failures
Problem: AuthenticationException: Username and/or password are incorrect
Cause: PasswordAuthenticator mismatch
Solution:
# Check HeliosDB authentication configurationheliosdb config get auth.authenticator
# Should output: PasswordAuthenticator
# Reset admin passwordheliosdb user reset-password adminApplication Fix:
from cassandra.auth import PlainTextAuthProvider
# Ensure correct username/passwordauth = PlainTextAuthProvider(username='admin', password='correct_password')cluster = Cluster(['heliosdb.example.com'], auth_provider=auth)3. Performance Degradation
Problem: Queries slower in HeliosDB than Cassandra
Diagnosis:
-- Check query planEXPLAIN SELECT * FROM users WHERE email = 'alice@example.com';Solution 1: Missing Indexes
-- Create secondary indexCREATE INDEX ON users (email);Solution 2: Optimize Consistency Level
# Use lower consistency for read-heavy workloadssession.default_consistency_level = ConsistencyLevel.LOCAL_ONESolution 3: Enable Query Cache
-- Enable intelligent caching (HeliosDB feature)ALTER SYSTEM SET intelligent_cache = 'on';ALTER SYSTEM SET cache_policy = 'ml_hybrid';4. Data Type Mismatch
Problem: Collection data not readable after migration
Cause: Frozen vs. non-frozen collections
Solution:
-- Check table schemaDESC TABLE my_keyspace.users;
-- If collections are frozen, they're immutable-- Recreate table with non-frozen collections if neededCREATE TABLE users_v2 ( user_id UUID PRIMARY KEY, tags SET<TEXT>, -- Non-frozen (mutable) metadata MAP<TEXT, TEXT> -- Non-frozen (mutable));5. Timeout Errors
Problem: OperationTimedOut: Operation timed out - received only 0 responses
Cause: Network latency, overloaded cluster, or large result set
Solution:
# Increase timeoutfrom cassandra.cluster import Cluster, ExecutionProfile
profile = ExecutionProfile( request_timeout=30.0 # Increase from default 10s)
cluster = Cluster(['heliosdb.example.com'], execution_profiles={EXEC_PROFILE_DEFAULT: profile})For Large Queries:
# Use paging for large result setsfrom cassandra.query import SimpleStatement
stmt = SimpleStatement("SELECT * FROM large_table", fetch_size=1000)for row in session.execute(stmt): process(row)6. Connection Pool Exhausted
Problem: NoHostAvailable: Unable to complete the operation against any hosts
Cause: Too many concurrent connections
Solution:
# Increase connection pool sizefrom cassandra.cluster import Cluster
cluster = Cluster( ['heliosdb.example.com'], protocol_version=5, executor_threads=4, # Increase thread pool max_schema_agreement_wait=10, control_connection_timeout=10, idle_heartbeat_interval=30, compression=True)Best Practices
1. Start with Non-Production Environments
Recommended Progression:
- Development (1-2 days): Test basic functionality
- Staging (1 week): Full integration testing
- Canary Production (1 week): 10% traffic to HeliosDB
- Production Rollout (2 weeks): Gradual 10% → 25% → 50% → 100%
2. Use Dual-Write for Critical Systems
Advantages:
- Zero downtime
- Easy rollback
- Gradual confidence building
Implementation: See Strategy 1: Dual-Write
3. Monitor Replication Lag During Migration
Key Metrics:
- Replication lag (target: <1 second)
- Write throughput (both clusters)
- Read latency (both clusters)
- Error rates
Monitoring Script:
#!/bin/bashwhile true; do # Check replication lag LAG=$(curl -s http://debezium:8083/connectors/cassandra-heliosdb/status | jq '.lag_seconds')
# Check write throughput CASSANDRA_WRITES=$(nodetool tpstats | grep 'MutationStage' | awk '{print $5}') HELIOSDB_WRITES=$(heliosdb stats writes)
# Print dashboard clear echo "=== Migration Monitor ===" echo "Replication Lag: ${LAG}s" echo "Cassandra Writes: ${CASSANDRA_WRITES}/s" echo "HeliosDB Writes: ${HELIOSDB_WRITES}/s" echo "========================"
sleep 5done4. Keep Cassandra as Fallback Initially
Recommendation: Keep Cassandra cluster running for 1-2 weeks after cutover
Rollback Preparation:
# Keep Cassandra config readily availableexport CASSANDRA_HOST_PRIMARY=heliosdb.example.comexport CASSANDRA_HOST_FALLBACK=cassandra.example.com
# Quick rollback scriptcat > rollback.sh <<'EOF'#!/bin/bashkubectl set env deployment/my-app CASSANDRA_HOST=$CASSANDRA_HOST_FALLBACKkubectl rollout restart deployment/my-appEOFchmod +x rollback.sh5. Test Rollback Procedure
Before Cutover:
# Test rollback in staging1. Switch to HeliosDB2. Verify application works3. Execute rollback script4. Verify application still works with Cassandra6. Document Your Migration
Migration Runbook Template:
# Migration Runbook: Cassandra → HeliosDB
## Pre-Migration Checklist- [ ] HeliosDB cluster provisioned and tested- [ ] Schema migrated and validated- [ ] Data migration method selected- [ ] Rollback procedure tested- [ ] Monitoring dashboards configured- [ ] On-call team notified
## Migration Steps1. [ ] Enable dual-write (or start replication)2. [ ] Begin data backfill3. [ ] Validate data consistency4. [ ] Route 10% read traffic to HeliosDB5. [ ] Monitor for 24 hours6. [ ] Route 50% read traffic to HeliosDB7. [ ] Monitor for 24 hours8. [ ] Route 100% traffic to HeliosDB9. [ ] Monitor for 1 week10. [ ] Decommission Cassandra
## Rollback Procedure1. Execute: ./rollback.sh2. Verify traffic routing to Cassandra3. Monitor error rates4. Investigate HeliosDB issue
## Success Criteria- Row counts match (100%)- Query latency < baseline + 10%- Error rate < 0.01%- No data lossRollback Plan
Scenario 1: Issues During Dual-Write Phase
Symptoms: Data inconsistency, high error rates
Action:
# 1. Stop dual-write# Comment out dual-write code or set environment variableexport ENABLE_DUAL_WRITE=false
# 2. Restart applicationkubectl rollout restart deployment/my-app
# 3. Continue writing to Cassandra only# 4. Investigate HeliosDB issuesheliosdb logs --tail 1000 | grep ERROR
# 5. Retry after fixesImpact: No downtime (still using Cassandra)
Scenario 2: Issues After Partial Cutover
Symptoms: Performance degradation, query errors
Action:
# 1. Immediately route all traffic back to Cassandrakubectl set env deployment/my-app CASSANDRA_HOST=cassandra.example.comkubectl rollout restart deployment/my-app
# 2. Verify application healthkubectl logs -f deployment/my-app
# 3. Analyze HeliosDB issuesheliosdb diagnose --export /tmp/diagnostics.tar.gz
# 4. Contact support if neededImpact: Brief downtime during restart (2-5 minutes)
Scenario 3: Data Loss Detected
Symptoms: Row count mismatch, missing records
Action:
# 1. IMMEDIATE ROLLBACK./rollback.sh
# 2. Stop all writes to HeliosDBheliosdb cluster pause --writes-only
# 3. Export HeliosDB data for forensicscqlsh heliosdb.example.com -e "COPY my_keyspace.users TO '/tmp/heliosdb_users.csv'"
# 4. Compare with Cassandradiff <(wc -l /tmp/cassandra_users.csv) <(wc -l /tmp/heliosdb_users.csv)
# 5. Re-run migration with identified fixesImpact: Rollback to Cassandra (5-10 minutes downtime)
Case Studies
Case Study 1: E-Commerce Platform (500M Daily Writes)
Customer: Large e-commerce company
Cassandra Setup:
- 30-node cluster
- 100 TB data
- 500M writes/day
- 2B reads/day
Migration Strategy: Dual-write
Timeline:
- Week 1: Schema migration, initial backfill
- Week 2: Dual-write enabled, 10% read traffic
- Week 3: 50% read traffic
- Week 4: 100% read traffic, write migration
- Week 5: Cassandra decommissioned
Results:
- Zero downtime
- 35% cost reduction
- 2.5x faster analytics queries
- No data loss
Key Success Factors:
- Comprehensive monitoring
- Gradual rollout
- 24/7 on-call support during migration
Case Study 2: IoT Sensor Network (10K Devices)
Customer: Industrial IoT platform
Cassandra Setup:
- 6-node cluster
- 20 TB time-series data
- 10K devices × 1 msg/sec = 10K writes/sec
Migration Strategy: Replication-based
Timeline:
- Day 1: Schema migration
- Day 2-3: Initial data replication (20 TB)
- Day 4: Replication caught up (lag < 1s)
- Day 5: Cutover (3-minute downtime)
- Day 6-12: Monitoring
Results:
- 3-minute downtime
- 50% cost reduction (tiered storage)
- 10x faster downsampling queries
- Successful migration
Key Success Factors:
- Low downtime tolerance (not 24/7 critical)
- Time-series data (less complex than transactional)
- HeliosDB edge sync for IoT devices
Case Study 3: SaaS Multi-Tenant Application
Customer: B2B SaaS provider (5000 tenants)
Cassandra Setup:
- 12-node cluster
- 50 TB data
- Multi-tenant (5000 tenants)
Migration Strategy: Tenant-by-tenant migration
Timeline:
- Week 1-2: Migrate 10 test tenants
- Week 3-4: Migrate 100 small tenants
- Week 5-6: Migrate 500 medium tenants
- Week 7-10: Migrate 4390 remaining tenants
Results:
- Zero downtime (per-tenant migration)
- 40% cost reduction
- Multi-protocol access (CQL + SQL)
- Tenant isolation improved
Key Success Factors:
- Tenant-by-tenant rollout reduced risk
- Automated migration tooling
- HeliosDB multi-tenancy features
Next Steps
1. Join HeliosDB Community
Resources:
- Documentation: https://docs.heliosdb.com
- GitHub: https://github.com/heliosdb/heliosdb
- Slack Community: https://heliosdb.slack.com
2. Schedule Migration Planning Call
Contact: migrations@heliosdb.com
Topics:
- Migration strategy selection
- Timeline estimation
- Resource requirements
- Risk assessment
3. Access Enterprise Features
Enterprise Add-Ons:
- 24/7 migration support
- Dedicated migration engineer
- Advanced monitoring and alerting
- Custom tooling development
- SLA guarantees
Contact Sales: sales@heliosdb.com
4. Training and Certification
HeliosDB Academy:
- Cassandra to HeliosDB Migration (4-hour course)
- HeliosDB Administration (8-hour course)
- Multi-Protocol Database Design (4-hour course)
Register: https://academy.heliosdb.com
Appendix A: Glossary
| Term | Definition |
|---|---|
| CQL | Cassandra Query Language |
| Keyspace | Top-level data container (similar to database) |
| Partition Key | Column(s) determining data distribution across nodes |
| Clustering Key | Column(s) determining sort order within partition |
| Consistency Level | How many replicas must respond to a query (ONE, QUORUM, ALL) |
| LWT | Lightweight Transactions (compare-and-set operations) |
| UDT | User-Defined Type (custom data type) |
| TTL | Time-to-Live (automatic data expiration) |
| SSTable | Sorted String Table (Cassandra’s on-disk format) |
| Compaction | Background process to merge SSTables |
Appendix B: Client Driver Compatibility
| Driver | Version | HeliosDB Compatibility |
|---|---|---|
| DataStax Python Driver | 3.25+ | 100% compatible |
| DataStax Java Driver | 4.15+ | 100% compatible |
| DataStax C++ Driver | 2.16+ | 100% compatible |
| DataStax Node.js Driver | 4.6+ | 100% compatible |
| DataStax C# Driver | 3.18+ | 100% compatible |
| GoCQL | 1.0+ | 100% compatible |
| Rust Driver (Scylla) | 0.9+ | 100% compatible |
| cqlsh | 5.0.1+ | 100% compatible |
Appendix C: HeliosDB-Specific Enhancements
1. SQL Interface on CQL Data
-- Query Cassandra data with SQLSELECT u.username, COUNT(o.order_id) AS order_countFROM my_keyspace.users uLEFT JOIN my_keyspace.orders o ON u.user_id = o.user_idGROUP BY u.usernameHAVING COUNT(o.order_id) > 10ORDER BY order_count DESC;2. Intelligent Query Caching
-- Enable ML-based query caching (HeliosDB feature)ALTER SYSTEM SET intelligent_cache = 'on';
-- Cached queries are automatically faster on subsequent runsSELECT * FROM large_table WHERE status = 'active'; -- 500ms (first run)SELECT * FROM large_table WHERE status = 'active'; -- 2ms (cached)3. Multi-Protocol Access
# Access same data via CQL and PostgreSQL protocolsfrom cassandra.cluster import Clusterimport psycopg2
# CQL protocolcql_cluster = Cluster(['heliosdb.example.com'], port=9042)cql_session = cql_cluster.connect('my_keyspace')cql_session.execute("INSERT INTO users (user_id, name) VALUES (?, ?)", [uuid4(), 'Alice'])
# PostgreSQL protocol (same data!)pg_conn = psycopg2.connect(host='heliosdb.example.com', port=5432, database='my_keyspace')pg_cursor = pg_conn.cursor()pg_cursor.execute("SELECT * FROM users WHERE name = %s", ['Alice'])print(pg_cursor.fetchall())Document Information
Version: 1.0 Last Updated: November 11, 2025 Maintainers: HeliosDB Migration Team Feedback: migrations@heliosdb.com
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