Counter Service: How we rewrote it in Rust

Summary

The Integrity Data Platform team rewrote Counter Service, a high-QPS Golang microservice that consumes streams, writes counts to Scylla, and exposes gRPC queries backed by Scylla and Redis. They selected it because BatchRead reached tens of thousands of QPS while remaining constrained in functionality, making infrastructure savings potentially worth the rewrite effort and Rust learning curve. Rather than translating code line by line, the team treated the existing service as a black box, preserved its interfaces and contracts, and rebuilt the application logic from scratch; it also assessed Rust ecosystem support for dependencies including tonic, Actix Web, Fred, and the Scylla driver. The rewrite delivered similar performance with 70% infrastructure savings, according to the abstract. The conclusion reports the service as 80% cheaper, endorses Rust for new services, and cautions that async Rust is challenging.

Takeaways

1. 1

   Counter Service’s BatchRead path served up to tens of thousands of QPS and queried counters through gRPC from Scylla and Redis.

2. 2

   The rewrite used a contract-first black-box approach instead of direct code conversion, aiming for outputs as close as possible to the original service.

3. 3

   The reported outcome was similar performance with 70% infrastructure savings in the abstract; the conclusion separately describes the service as 80% cheaper and warns that async Rust can be difficult.