year
2024 — 2025
role
principal engineer
client
internal infra · series-B fintech
stack
Rust · Yrs (Y-CRDT) · WASM
haku (白, 'blank canvas') is a CRDT-backed realtime engine powering collaborative compliance workflows for a fintech handling $4B in annual settlement.
ch · 01
why rust
the previous Node sync layer collapsed at 200 concurrent docs. we needed predictable latency under regulator scrutiny — rust + tokio gave us p99 under 18ms at 5k concurrent peers.
ch · 02
architecture
Yrs as the CRDT primitive, compiled to WASM for the browser, native binaries for desktop. NATS JetStream as the durable log, Postgres for snapshots. zero merge conflicts in 9 months of production.
ch · 03
impact
shipped to 14k seats. reduced sync infra cost 71%. enabled the company's first multi-region compliance product.
/ outcomes
concurrent peers
5k
p99 sync
18ms
infra cost
−71%
seats
14k
/ stack