quaint VS rusqlite

That is only used in tests :) The query engine uses this: https://github.com/prisma/quaint/blob/6532d69b5aec007ad06ac6...

(I work at Prisma, could have mentioned that earlier)

Just a quick note about this point: We do use the standard Rust drivers for the DBs we support (e.g. tokio-postgres or the official MongoDB driver for Rust) and don't write/maintain our own drivers, you can see this from our Cargo.toml.

I'm using https://github.com/prisma/quaint/ with mssql. As far as I understand, it wasn't released to crates.io for two year only because of some dependencies issues with postgres (https://github.com/prisma/quaint/issues/264)

"Rusqlite is an ergonomic wrapper for using SQLite from Rust." - Crates.io

If you're less concerned about the "structure" of your data (e.g., serializing into rust types) and just need tabular data that can be queried (e.g., how much did we bet on X date, who placed a bet on Y team, etc.) I would definitely lean more towards a SQLite database for that kind of work. rusqlite can get you a functional database fairly quickly with a little reading of the documentation (be sure to use the "bundled" feature).

Create a connection per task. WAL is probably a good idea.

Even using SERIALIZED mode, sqlite has multiple APIs which are completely broken if two clients touch the same connection (https://github.com/rusqlite/rusqlite/issues/342#issuecomment...).

Don't bother, just don't share connections between threads and use the regular multi-thread mode (do use that though).

It fails your "ship with a crate" requirement, but when it comes to "csv but too small for a database" it's always worth having a think about SQLite. Of note, the rusqlite crate with the bundled feature will download, compile, and link against sqlite.

You may want to read the Readme of Rusqlite, especially the Optional Features.

As far as I know, the only option for an embedded SQL database is SQLite. The most actively maintained one, for rust, seems to be rusqlite (https://github.com/rusqlite/rusqlite).

Yes, but it's readonly. Also they did not merge loadable extensions support, which I need - https://github.com/rusqlite/rusqlite/pull/910

rusqlite 0.27.0, which looks like it's still the latest version

SQLite is written in C, while workers is based on V8 isolates, so it mainly runs JavaScript. Fortunately, it also supports running WASM through initialising and calling WASM modules via JavaScript. Emscripten can be used to build WASM from C, but I'd rather use it through Rust (using rusqlite), so this is what I focus on right away. Workers can also be written entirely in Rust using worker-rs.