# workerd error: vectorize query topk too large

## TL;DR

The query asked for more results than the topk limit allows. Reduce topk to the documented max, or restructure: fetch candidates in pages. Topk is bounded because the math gets expensive.

```text
workerd error: vectorize query topk too large
```

## Steps

1. Check the requested topk against the documented limit.
   Expected: The overage is confirmed.

2. Reduce topk to within the limit.
   Expected: The query succeeds.

3. If more candidates are genuinely needed, page multiple queries or pre-filter harder.
   Expected: The need is met within limits.

4. Settle on a default topk for the app and enforce it in the query builder.
   Expected: Overlarge requests stop.

5. Monitor topk values in production queries.
   Expected: Usage stays sane.

## When to use

- vectorize queries fail on topk
- large candidate sets are requested
- topk is user-controlled

## When not to use

- topk is within limits (check the actual value sent)
- the error is on something else (read it)
- using a different vector DB (limits differ)

## Tool compatibility

- workerd
- Vectorize

## Variant phrasings

- "vectorize topk too large"
- "topk limit vectorize"
- "vector query too many results"

## Why it happens

Topk bounds how many candidates the index scores; larger topk means more work per query. The platform caps it to protect latency. Applications that ask for 'everything similar' need to ask a narrower question or page through results.

## Edge cases

- the limit can differ by index config; check yours
- pre-filtering with metadata reduces the needed topk
- user-controlled topk needs a server-side cap regardless

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_ZtEtfcSfVEU908xvWXi_mQ