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## Summary Five changes that take load off the writer pool and the relay's connection bookkeeping. On a single-relay load rig, the clean ceiling moves from 40k to about 48k WebSocket clients. In the A/B, connect p99 at 48k fell from 4.1 s (abort) to 1.65 s. 1. **Ban/mute restriction cache with a 1 s max age.** HTTP API requests, publishes and ephemeral writes read `(community, pubkey)` restriction state through one cache. An entry is served for 1 s from when its read began, matching the open-channel cache's bound. Socket admission, moderation-command actor checks and the `/buzz/v1` ban recheck still read fresh. An admitted socket outlives the 1 s window, so a banned client that reconnects inside it would otherwise keep a socket open indefinitely. A ban drops the target's entry, and each owned agent's entry, on every pod as part of the live-disconnect fan-out, best-effort. Timeouts, untimeouts and unbans drop it on the pod that handles them. 2. **Fewer round trips per event read.** Replica reads skip the per-read `statement_timeout` tighten, because the reader pool installs the deadline at connect. They keep the savepoint, so a failed or cancelled read leaves the session usable and releases its locks. That takes them from 4 round trips to 3. Writer reads send `BEGIN` and the tighten as one message, which also takes them from 4 to 3. 3. **Concurrent open-channel cache misses share one read.** The first miss in a community takes a per-community gate and reads; the others wait for it and use its result. A waiter whose leader failed reads once on its own and does not queue again. A waiter also stops waiting after the cache's 1 s max age and reads on its own, because the leader's set would be stale by then anyway. So a leader whose read hangs stalls only its own request. 4. **`has_admitted_connection` is one map lookup.** A `(community, pubkey) → admitted count` index is maintained under each socket's pubkey lock in `mark_admitted`, `set_authenticated_identity` and `deregister`. It replaces a scan of every connection on each disconnect. 5. **Host → community cache with a 1 s max age.** Only successful lookups are cached; unmapped hosts and errors go to the database every time. ## What got simpler - The ban handler's separate pod-local cache drop is gone; the disconnect every ban already runs covers it on every pod. - One write-restriction gate instead of two. `enforce_cached_write_restriction`, `enforce_relay_membership_ephemeral` and the `cached_ban` parameter chain through `enforce_membership` / `admit_member` / `deny_banned` are deleted. - The ephemeral path's separate 30 s ban cache is gone, so the relay has one staleness rule for restriction state instead of two. ## Notes - Bans reach the restriction cache on every pod. Every ban path (signed command, report action, relay admin) closes the target's and its agents' sockets clusterwide, and each pod drops those entries in the same step. A dropped Redis publish, or a restriction read already in flight when the drop lands (it can refill the old row), falls back to the 1 s bound. Timeouts on other pods also rely on the 1 s bound, and so do unbans and untimeouts, which fail closed. - On the load rig the restriction-cache hit rate was 28%, because HTTP agents poll every 5 s. A longer TTL with Redis invalidation would raise it, but that is a separate change. ## Load test Single relay pinned to 8 cores, native Postgres 16, a seeded fixture with 2,000 open channels, and a 6-shard generator. Steady ramp with 120 s holds; a step aborts at p99 > 3 s. Each step adds 10% HTTP agents. | clients | base connect p99 | this PR connect p99 | base relay cores | this PR relay cores | |---|---|---|---|---| | 32k | 34 ms | 31 ms | 1.71 | 1.66 | | 40k | 45 ms | 26 ms | 2.33 | 2.15 | | 48k | 4,107 ms (abort) | 1,652 ms | 4.7 | 3.0 | | 56k | n/a | 4,535 ms (abort) | n/a | 4.0 | Open-channel re-reads over the run fell from 72k to 1.6k. The tenant cache hit rate was 94%. 48k is this branch's knee. A later run of the same build aborted at 48k: connect p99 2.2 s, but 29% subscribe errors from the concurrent-handler cap. With a 10 s restriction max age, it passed 48k, at connect p99 1.56 s, 60% hit rate and 10% fewer relay cores, and both arms stopped at 56k. ## Testing - `cargo fmt --check`, `cargo clippy -p buzz-relay -p buzz-db --all-targets -D warnings` - `cargo test -p buzz-db --lib` and `-p buzz-relay --lib`, run in parallel. The only failures were 8 DB-seeding tests that need a migrated default database; the Postgres lane covers them. Commits after that run changed the replica savepoint, the `/buzz/v1` recheck revert and some test edits. - Postgres lane at head: `scripts/postgres-test-run.sh -p buzz-relay -p buzz-db --lib --bins --tests`. All 1,183 tests passed. - Mutants. Each one must turn its new test red: - waiters skipping the gate - a no-op index removal - the tenant cache ignoring age - the restriction cache ignoring age - a waiter waiting on the gate with no limit - a disconnect that keeps the cached restriction row - replica reads dropping the savepoint buzz-review-completed 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Signed-off-by: Luke Tornquist <tornquist@squareup.com> Co-authored-by: Elrond <28d6302a099e5225b02c4155ac4236e4912603df2ab08dbfc2f4fef08ce598c8@buzz.block.builderlab.xyz> Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>