HeliosDB Protocol Compatibility Matrix

Unified compatibility reference for HeliosDB Full’s protocols. HeliosDB Full opens listeners for PostgreSQL, MySQL, Oracle, MongoDB, Cassandra, Redis and SQL Server plus an HTTP gateway; MongoDB, Cassandra and SQL Server clients can connect and authenticate, and reading and writing HeliosDB tables through them is planned. See the protocol hub for ports, flags and credentials.

Storage-backed: PostgreSQL, MySQL, Oracle and the HTTP gateway (POST /api/v1/query) read and write the shared tables.
In memory: the Redis listener keeps its keyspace in memory; it is not persisted to HeliosDB tables.
Connect and authenticate only: MongoDB, Cassandra and SQL Server clients can connect and authenticate; reading and writing HeliosDB tables through them is planned. Standard Cassandra drivers (DataStax drivers, cqlsh) cannot connect yet.
Planned, no listener: GraphQL, Snowflake, Databricks, ClickHouse, DB2 (DRDA), Pinecone and an S3-compatible object API. The HTTP gateway answers /snowflake/, /dbsql/ and /pinecone/ with 501 Not Implemented.
TLS: HeliosDB Full listeners do not terminate TLS; put a TLS-terminating proxy in front. Native PostgreSQL TLS is planned for the next release.
MongoDB authentication: the MongoDB listener accepts SCRAM-SHA-256 only; set authMechanism=SCRAM-SHA-256.

The coverage figures in the per-protocol sections below describe the design target; where they disagree with this list, this list describes the current release.

Protocol Overview

Protocols

Protocol	Port	Version	Compatibility	Result	Documentation
PostgreSQL	5432	17	100%	Supported	postgresql/
MySQL	3306	v10	80%+	Supported	mysql/
MongoDB	27017	6.0+/8.0	Connects and authenticates; reads and writes of HeliosDB tables planned (compatibility notes)	Handshake and auth	mongodb/
Redis	6379	RESP3	In-memory keyspace, not persisted	In memory	redis/
Cassandra	9042	v4/v5	Connects and authenticates; reads and writes of HeliosDB tables and standard-driver connections planned (compatibility notes)	Handshake and auth	cassandra/
HTTP/REST	8443 (plain HTTP)	HTTP/1.1	`POST /api/v1/query`	Supported	http-rest/
GraphQL	—	—	Planned; no listener in `heliosdb-full`	Planned	graphql/
Snowflake	—	—	Planned; `/snowflake/` paths answer 501	Planned	snowflake/
ClickHouse	—	—	Planned; no listener in `heliosdb-full`	Planned	clickhouse/

Additional Protocols

Protocol	Port	Version	Compatibility	Result
Oracle	1521	23ai	Core data access; Oracle-specific syntax and PL/SQL need rewriting (in-house applications)	Supported
SQL Server (TDS)	1433	—	Connects and authenticates; reads and writes of HeliosDB tables planned	Handshake and auth
DRDA/DB2	—	—	Planned; no listener in `heliosdb-full`	Planned
Pinecone	—	—	Planned; `/pinecone/` paths answer 501	Planned
S3-compatible object API	—	—	Planned; no listener in `heliosdb-full`	Planned

Quick Comparison

Feature	PostgreSQL	MySQL	MongoDB	Redis	HTTP/REST	GraphQL
Wire Protocol	v3.0	v10	OP_MSG	RESP3	HTTP/1.1	HTTP
Authentication	SCRAM-256	SHA2	SCRAM-256	AUTH	API key (Bearer)	Bearer/JWT
Transactions	ACID	ACID	ACID	Multi	-	-
Replication	Planned (with clustering)	Planned (with clustering)	Change streams planned	Pub/Sub (in memory)	-	Subscriptions planned
Compression	Yes	Yes	Yes	-	gzip/br	gzip/br

PostgreSQL 17

Feature Coverage: 100%

Category	Coverage	Key Features
Wire Protocol	100%	v3.0 complete
SQL Language	95%+	Full SQL support
Data Types	100%	All standard types
Transactions	100%	MVCC, isolation levels
Replication	Planned	Logical and physical replication are planned with clustering

PostgreSQL 17-Specific

JSON_TABLE function
MERGE with RETURNING
COPY with ON_ERROR
Incremental backup (planned)
Slot failover (planned with clustering)

Details: postgresql/

MySQL

Feature Coverage: 80%+

Category	Coverage	Key Features
Wire Protocol	100%	v10 complete
SQL Language	85%+	Standard MySQL syntax
Data Types	100%	All MySQL types
Transactions	100%	InnoDB-compatible
JSON	100%	JSON functions

Key Capabilities

ON DUPLICATE KEY UPDATE (upsert)
SHOW commands (DATABASES, TABLES, etc.)
AUTO_INCREMENT columns
LOAD DATA INFILE
Multi-statement queries

Details: mysql/

MongoDB 6.0+/8.0

Feature Coverage: 100%

Category	Coverage	Key Features
Wire Protocol	100%	OP_MSG complete
BSON Types	100%	All 17 types
CRUD	100%	All operations
Aggregation	100%	MongoDB 8.0 stages
Transactions	100%	SERIALIZABLE

Key Capabilities

Full aggregation pipeline (planned with storage-backed reads)
Change streams via CDC (planned)
All query operators (planned with storage-backed reads)
Index management (planned)
GridFS and capped collections: not supported; both are planned

Details: mongodb/

Redis RESP3

Feature Coverage: 90%

Category	Coverage	Key Features
RESP Protocol	100%	RESP3 complete
Data Structures	100%	All types
Pub/Sub	100%	Full support
Streams	100%	Consumer groups
Scripting	80%	Lua scripts

Key Capabilities

Strings, Lists, Sets, Hashes, Sorted Sets
Pipelining and transactions
Pub/Sub messaging
Key expiration (TTL)
Cluster mode (planned with clustering)

Details: redis/

Cassandra CQL v4/v5

Feature Coverage: 100%

Category	Coverage	Key Features
Native Protocol	100%	v4, v5 complete
Data Types	100%	All CQL types
CQL Language	100%	Full support
Batch Operations	100%	All batch types
LWT	100%	IF conditions

Key Capabilities

Wide-column mapping
TTL support
Compression (LZ4, Snappy)
Prepared statements
Event notifications

Details: cassandra/

HTTP/REST API

What the HTTP gateway serves

Category	State	Details
HTTP Protocol	Available	HTTP/1.1, plain HTTP on port 8443
Authentication	Available	API key from `HELIOSDB_API_KEY`, sent as `Authorization: Bearer` or `X-API-Key`
Query Endpoint	Available	`POST /api/v1/query` runs SQL against the shared tables
AI Endpoints	Available	`/v1/chat/completions`, `/api/v1/embeddings`, `/api/v1/vectors/stores`, `/api/v1/agents/memory`, `/api/v1/documents`
CRUD Endpoints	Planned	Table operations without SQL
Streaming	Planned	SSE, WebSocket

Key Capabilities

SQL over HTTP: POST /api/v1/query over HTTP/1.1
Health and readiness probes: /health, /ready, /status
Rate limiting and throttling
Databricks SQL and Pinecone compatibility APIs: planned; today /dbsql/ and /pinecone/ answer 501 Not Implemented

Details: http-rest/

GraphQL

Feature Coverage: 80%+

Category	Coverage	Key Features
Queries	100%	Full query support
Mutations	100%	Insert/Update/Delete
Subscriptions	100%	Real-time updates
Federation	100%	Apollo Federation v2
Introspection	100%	Schema discovery

Key Capabilities

Auto-generated schema from tables
Relay-style connections
Query batching and DataLoader
Query complexity analysis
Interactive playground

Details: graphql/

Snowflake

Feature Coverage: 90%+

Category	Coverage	Key Features
SQL API	100%	Statement execution
Time Travel	100%	AT/BEFORE syntax
VARIANT	100%	Semi-structured data
FLATTEN	100%	Array/object unnesting
Warehouses	100%	Virtual compute

Key Capabilities

Time travel queries
VARIANT data type with path notation
COPY INTO for bulk loading
Virtual warehouse management
Session management

Details: snowflake/

ClickHouse

Feature Coverage: 85%

Category	Coverage	Key Features
Native Protocol	85%	TCP 9000
HTTP Interface	100%	Port 8123
SQL	90%	ClickHouse SQL
Table Engines	80%	MergeTree family

Key Capabilities

Columnar storage mapping
Aggregation functions
Array operations
Approximate functions
OLAP optimizations

Details: clickhouse/

Additional Protocols

Oracle 23ai

HeliosDB Full’s Oracle compatibility module covers a large part of Oracle’s feature surface; through the Oracle listener today, core data access runs unchanged (see Oracle compatibility for in-house applications for results by usage area). Module status by category:

Category	Status
Core SQL	Supported
PL/SQL Core	Beta in the module; execution through the Oracle listener on the roadmap
Hierarchical	Supported
Analytic Functions	Supported
DBMS Packages	Partial

Details: oracle/

DRDA/DB2 (95%)

Category	Coverage
DRDA Protocol	95%
SQL Language	95%
Stored Procs	85%

Details: drda/

Pinecone Vector (100%)

Category	Coverage
REST API	100%
Vector Operations	100%
Filtering	100%

Details: pinecone/

Driver Compatibility Matrix

Driver	PostgreSQL	MySQL	MongoDB	Redis	Cassandra
Python	psycopg2/3	mysql-connector	PyMongo	redis-py	cassandra-driver
Node.js	node-postgres	mysql2	mongodb	ioredis	cassandra-driver
Java	JDBC	JDBC	MongoDB Driver	Jedis	DataStax
Go	lib/pq	go-sql-driver	mongo-go	go-redis	gocql
Rust	rust-postgres	mysql	mongodb	redis-rs	-
C#	Npgsql	MySqlConnector	MongoDB.Driver	StackExchange.Redis	CassandraCSharpDriver

MongoDB drivers: connection and authentication only, for now; reading and writing HeliosDB tables through them is planned. Cassandra drivers: the standard drivers listed above cannot connect to the listener yet; support for them, and CQL reads and writes of HeliosDB tables, are planned. Redis drivers reach the listener’s in-memory keyspace, which is not persisted.

Performance Comparison

Query overhead per protocol (internal tests, HeliosDB Full, each protocol vs the PostgreSQL wire path as the baseline):

Protocol	Handshake	Auth	Query Overhead
PostgreSQL	1 RTT	1-2 RTT	Baseline
MySQL	1 RTT	1 RTT	+2%
MongoDB	1-2 RTT	1-2 RTT	+5%
Redis	1 RTT	1 RTT	-10%
HTTP/REST	0 RTT (keepalive)	0 RTT (header)	+8%
GraphQL	0 RTT (keepalive)	0 RTT (header)	+10%
Cassandra	1 RTT	1 RTT	+3%

Migration Paths

From	To HeliosDB	Changes Required
PostgreSQL	Direct	None - fully compatible
MySQL	Direct	Connection string only
MongoDB	Planned	Storage-backed reads and writes are planned
Redis	Cache only	In-memory keyspace, not persisted
Cassandra	Planned	Storage-backed reads and writes and standard-driver connections are planned
Oracle	Moderate	Connection string, verify PL/SQL
SQL Server	Planned	Table reads and writes over TDS are planned

Testing Coverage

Protocol	Unit Tests	Integration	Edge Cases	Total
PostgreSQL	200+	50+	100+	350+
MySQL	150+	40+	60+	250+
MongoDB	150+	40+	60+	250+
Redis	120+	30+	50+	200+
Cassandra	100+	30+	40+	170+
HTTP/REST	80+	25+	30+	135+
GraphQL	100+	30+	40+	170+
Snowflake	80+	20+	30+	130+
ClickHouse	60+	20+	25+	105+

Listeners in HeliosDB Full: 8 (7 database wire protocols plus the HTTP gateway)