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buzz/crates/buzz-relay
Tom Brow b8b1ab5b3c perf(push): avoid empty push delivery claims (#8524)
Each enabled push delivery worker currently opens a claim transaction
for every active community, even when its queue is empty. Discover
eligible communities in bounded pages first, then use the existing claim
and delivery path.

No schema or index change is needed. Per-delivery optimizations (sharing
serving-write leases across a batch and combining revalidation or
membership checks), enqueue batching, and outbox pruning are out of
scope and are being investigated separately, including their deletion,
revocation, and stale-worker safety guarantees.

### Related issue

No matching existing issue or PR found.

### Validation

- 25 focused PostgreSQL tests passed, covering real-worker delivery,
eligibility filtering, pagination fairness, concurrent claims,
expired-claim recovery, and stale-worker fencing. The [full PostgreSQL
CI
suite](https://github.com/block/buzz/actions/runs/39675698081/job/119490943190)
passed all 1,090 tests, including all seven new regressions.
- Discovery was benchmarked with **43,000 communities**, existing
indexes, and 30 warm executions per scenario. Empty queues required no
community lookups; eight ready communities spread across the ID range
required eight community index lookups. Results and the
alternative-query comparison are below.
- In the separate real-worker test with 1,000 empty communities, the
original worker made 1,401 claim admissions in 1.8 seconds; the fixed
worker made zero. One and four workers made 3 and 12 discovery reads
respectively.
- In the delivery test with 65 ready communities plus 1,000 empty
communities, all 81 notifications reached an HTTP test gateway in 0.83
seconds versus 1.55 seconds with the original loop.
- Independent standards and specification reviews, plus [Codex
review](https://github.com/block/buzz/pull/8524#issuecomment-6326568721),
found no remaining blockers. Final Rust linting, the full local
unit/integration run, desktop JavaScript tests/build, web build, and
mobile analysis/tests passed. The full local desktop test run had one
unrelated timing failure in `reaps_descendant_on_timeout`; its isolated
recheck passed.
[CI](https://github.com/block/buzz/actions/runs/39675698081) passed,
including the Windows retry after an unrelated subprocess timeout.

These are isolated local measurements, not production latency guarantees
or a simulation of full production concurrency. Production delivery
validation remains part of the release process; this PR does not
re-enable push or deploy the change.

### Alternative considered

An outbox-first query selects due pending jobs and expired sending jobs
with `UNION ALL`, applies the same eligibility checks, then returns
distinct community IDs. This could avoid scanning communities with no
ready work. However, the current query's `EXISTS` clause does not force
PostgreSQL to probe the outbox once per community: the measured plans
already avoid that work when queues are empty.

Both query shapes were tested against the same **43,000-community**
dataset using existing indexes. Median database execution times over 30
warm runs:

| Scenario | Current query | Outbox-first query |
| --- | ---: | ---: |
| Empty outbox | 0.038 ms | 0.041 ms |
| No ready work, 27,336 retained jobs | 0.060 ms | 0.066 ms |
| Eight ready communities spread across the ID range, including expired
sending jobs, plus retained history | 0.109 ms | 0.126 ms |
| Eight ready communities, 128 invalid jobs, and 27,200 terminal jobs |
0.225 ms | 0.335 ms |

Both queries returned identical community IDs in every scenario. Forced
generic prepared plans produced similar results. The current query was
retained because the alternative did not reduce measured execution time
or eliminate a community scan present in the empty-queue plan. No query
rewrite or additional index was justified by these measurements.

---------

Signed-off-by: Tom Brow <tomb@block.xyz>
2026-10-26 10:24:25 -07:00
..