FastAPI With SQLite

January 10, 2026

Trying to get FastAPI to work with asynchronous queries to an SQLight database (rough notes).

EDIT: I was onto something with Depends(), but the way I’ve got things setup here would create an AsyncHttpClient for each request. A better approach is outlined at notes / FastAPI with Chroma.

FastAPI dependencies — Depends()

https://fastapi.tiangolo.com/reference/dependencies/#depends

Dependencies are handled with the special function Depends() that takes a callable:

from fastapi import Depends

fastapi.Depends signature:

Depends(dependency=None, *, use_cache=True, scope=None)

Don’t call it directly, FastAPI calls the dependency function:

async def get_db_connection() -> aiosqlite.Connection | Any:
    db = await aiosqlite.connect(db_path)
    db.row_factory = aiosqlite.Row

    try:
        yield db
    finally:
        await db.close()


@app.post("/query", response_class=HTMLResponse)
async def query_collection(
    query: Annotated[str, Form()],
    db: aiosqlite.Connection = Depends(get_db_connection, scope="function"),
):
    cursor = await db.execute("SELECT html_heading FROM sections")
    row = await cursor.fetchone()
    print(row[0]) if row else None

Read the docs ( https://fastapi.tiangolo.com/reference/dependencies/#depends ) for details about the Depends() method’s params. Useful for my case:

scope: Mainly used for dependencies with yield, define when the dependency function should start (the code before yield) and when it should end (the code after yield).
- "function": the dependency function will be executed around the path operation function
- "request": the dependency function will be executed around the request and response cycle

Note that the yield expression on async def get_db_connection() causes the function to return an asynchronous generator function. See notes / The Python yield keyword (Yield expressions in async functions) for details.

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