Casual Office — Engineering notesTechnical posts from building open-source web spreadsheets, .docx editors, and slide decks. Yjs CRDT bridges, Hocuspocus, capacity modelling, .xlsx + .pptx round-trip, and the production-readiness work behind each release.https://schnsrw.live/en-usMeasuring the WebSocket broadcast ceiling of a single Node processhttps://schnsrw.live/notes/websocket-broadcast-ceiling-single-node-process/https://schnsrw.live/notes/websocket-broadcast-ceiling-single-node-process/We modelled the broadcast ceiling of a Hocuspocus + Yjs CRDT backend at ~500 active docs per Node process. Then we measured it. The model was 10× too conservative — the real bottleneck is somewhere else entirely.Thu, 28 May 2026 00:00:00 GMThocuspocusyjswebsocketload-testingcapacity-planningnodeLoad testing without k6: a 190-line Node-only HTTP harnesshttps://schnsrw.live/notes/http-load-harness-without-k6/https://schnsrw.live/notes/http-load-harness-without-k6/Before you reach for k6 or artillery, try a Node script. Built-in fetch + perf_hooks gives you p50/p95/p99 in 190 lines, zero new dependencies, and runs anywhere Node runs. Real numbers from the Casual Sheets v0.2.0 production-readiness pass.Thu, 28 May 2026 00:00:00 GMTload-testingnodefetchperfbenchmarkingcapacity-planningYjs replay retry: classifying transient vs permanent failures in a CRDT bridgehttps://schnsrw.live/notes/yjs-replay-retry-transient-vs-permanent/https://schnsrw.live/notes/yjs-replay-retry-transient-vs-permanent/When a Yjs CRDT bridge fails to apply a remote mutation, the difference between "network blip during chunk-load" and "malformed mutation params" matters a lot. We added a 50-line classifier and a 4-second retry budget. Silent divergences became user-visible recoverable state.Thu, 28 May 2026 00:00:00 GMTyjshocuspocuscrdterror-handlingcollaborative-editingproductionRate limiting and room caps for a Hocuspocus + Fastify backendhttps://schnsrw.live/notes/rate-limit-room-cap-hocuspocus-backend/https://schnsrw.live/notes/rate-limit-room-cap-hocuspocus-backend/A production-readiness pass on a Yjs realtime backend: per-route token-bucket rate limiting via @fastify/rate-limit, a MAX_ROOMS cap with two-pass LRU eviction, and a 503 capacity_full envelope. Three small pieces that turn "denial-of-service-by-loop" into "tight-but-bounded write surface."Thu, 28 May 2026 00:00:00 GMTfastifyhocuspocusrate-limitingproductionbackend-hardeningyjsWhen deepRewriteUnitId isn't deep enough: a Yjs CRDT bridge bughttps://schnsrw.live/notes/drawing-sync-json1-op-path/https://schnsrw.live/notes/drawing-sync-json1-op-path/A cross-peer drawing sync bug in a Yjs + Hocuspocus collaborative spreadsheet. The fix wasn't where we expected. A story about positional arrays, json1 op paths, and why "the skipped test header explains the bug" is a comforting lie.Wed, 27 May 2026 00:00:00 GMTyjshocuspocuscrdtcollaborative-editingbug-fixjson1