---
title: "Mode Selection Guide"
---

# Mode Selection Guide


This guide has been merged into a single canonical page so that there is one
description of how Nano is deployed rather than several competing ones.

**See [Deployment Modes](https://www.heliosdb.com/docs/nano/guides/deployment_modes/).** It covers, in one taxonomy:

- **Storage mode** — persistent vs. in-memory.
- **Access mode** — embedded library API, interactive REPL, foreground server,
  background daemon.
- How to choose, with the real CLI flags and configuration keys.
- Why a data directory is owned by exactly one process, and what that means for
  moving between modes.
- What running a server and a REPL side by side actually gives you (two
  processes, two separate data directories — not shared access to one dataset).

For what is safe to do from several callers at once, see
[Concurrency and transactions](https://www.heliosdb.com/docs/nano/guides/concurrency-and-transactions/).