Skip to content
Problems.

Trouble with Prefect concurrency

Data engineering3 posts from 2 people2d active+11 post in the last 7 days, 2 the 7 days before (steady)

Posts per day

Posts per day3 posts, Sep 23 to Oct 6

The posts behind it

3, newest first
PostDate
Concurrency limits page only fetches 200 limits### Bug summary # Description The Prefect UI `/v2/concurrency-limits` page loads the concurrency limits once, when the page opens, with no limit parameter. The server applies its default page size (PREFECT_SERVER_API_DEFAULT_LIMIT, 200), so the client never receives more than...PrefectHQ/prefectgsistelosOct 24 days ago
Cached task runs wait for a tag concurrency slot before the cache lookup### Bug summary When a task has a tag with a concurrency limit, the engine takes the tag's slot before it checks the cache. A task run that would come back Cached still waits for a slot behind the live runs holding the limit. Expected: returned Cached after 0.xxs Actual: cache...PrefectHQ/prefectDeltaEvoSep 2313 days ago
Releasing a concurrency slot doesn't wake waiters in the same process, so the slot sits idle until their Retry-After expires### Bug summary When a caller releases a concurrency slot, nothing tells callers waiting on the same limit in the same process. They keep sleeping until their Retry-After expires and only then ask again, so the slot sits unused in the meantime, even though the process just...PrefectHQ/prefectDeltaEvoSep 2313 days ago

Companies and products named

Company or productPosts naming it
Prefect3
About this problem

Evidence

3 posts from 2 people in 1 place, about 2 a week over 10 days. Mostly on PrefectHQ/prefect.

Frustration Frustration 0 of 3· Seen on GitHub issues

How it was grouped

Posts about Prefect with no known issue, sharing the word "concurrency". First post Sep 23, 2026, latest Oct 2, 2026. Corroborated: 3 or more posts from 2 or more people or places. Method

History

  • 2026-10-06 Added: Trouble with Prefect concurrency (3 posts)

Rising problems by email

Mondays: the problems in data, tech and AI that grew fastest that week.

Double opt-in. Unsubscribe any time.