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SQLite vs Alopex DB
SQLite's single file, two write modes, serializable isolation, and FTS5. Also explains how it differs from Alopex DB.
Updated: Oct 11, 2026
What SQLite is
SQLite is a self-contained SQL database engine with no server and no configuration. A library is embedded in the application and reads and writes one database file directly. The documentation says the library can be smaller than 900 KiB with all features enabled.
How it works
- File format: the whole database is one file. The project also publishes a document recommending it as an application file format.
- Atomic commit: the default is a rollback journal, which keeps a crash from leaving a half-written state.
- Append mode: changes are appended to a separate log file. Per the documentation, readers do not block writers and writers do not block readers. The cost is a checkpointing step, and all processes using the database must be on the same host.
- Isolation: SQLite transactions are SERIALIZABLE. Only one write transaction runs at a time.
Main features
- Flexibly typed tables, indexes, views, triggers, window functions, and CTEs.
- Extension modules. FTS5 is a full-text search virtual table. vec1 is SQLite’s official extension that adds vector search. sqlite-vec is a third-party alternative.
- Build-time limits are documented.
Limits
Sharing one file across hosts over a network is a weak point. Writes happen one at a time. It has no server and no authentication.
How it differs from Alopex DB
Both are SQL databases you embed in an application and use through a single database file. Alopex DB opens from Rust and Python in the same way.
On top of that simplicity, Alopex DB has a vector type and an HNSW index, full-text search, and an HTTP and gRPC server in the core. Embedding vectors and table data live in the same file and the same transaction, so you can build RAG and similarity search into an app with no second database.
| Aspect | SQLite | Alopex DB |
|---|---|---|
| File | One file | One .alopex file |
| Vector search | Added by the official vec1 extension or the third-party sqlite-vec extension | HNSW, exact search |
| Server | None | HTTP and gRPC |
| Sharing across hosts | Not suited (the documentation recommends a client/server database when many clients use it over a network) | Connect through the HTTP or gRPC server |
Alopex DB keeps the ease of SQLite and adds vector search and a server. The quickstart makes it easy to try.
References
- SQLite: About, Atomic Commit, Concurrent reads and writes, Isolation, Limits, FTS5, Application File Format, Release 3.54.0, Vec1 Vector Extension