Whirlwind – Async concurrent hashmap for Rust
Hey HN, this is Will and David from Fortress (https://news.ycombinator.com/item?id=41426998). We use a lot of async Rust internally, and created this library out of a need for an async-aware concurrent hashmap since there weren’t many available in the Rust ecosystem. Whirlwind is a sharded HashMap with a fully asynchronous API. Just as dashmap is a replacement for std::sync::RwLock, whirlwind aims to be a replacement for tokio::sync::RwLock. It has a similar design and performance characteristics to dashmap, but seems to perform better in read-heavy workloads with tokio's…
In plain words
Whirlwind is a sharded concurrent hashmap library for Rust with a fully asynchronous API. Built by developers at Fortress, it provides an async-aware alternative to wrapping hashmaps in tokio synchronization primitives. The library uses similar sharding design to dashmap but is optimized for read-heavy workloads in async contexts. It runs unsafe code verification through Miri in continuous integration and includes benchmark comparisons in its documentation.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
Hey HN, this is Will and David from Fortress (https://news.ycombinator.com/item?id=41426998). We use a lot of async Rust internally, and created this library out of a need for an async-aware concurrent hashmap since there weren’t many available in the Rust ecosystem. Whirlwind is a sharded HashMap with a fully asynchronous API. Just as dashmap is a replacement for std::sync::RwLock<HashMap>, whirlwind aims to be a replacement for tokio::sync::RwLock<HashMap>. It has a similar design and performance characteristics to dashmap, but seems to perform better in read-heavy workloads with tokio's green threading. Benchmarks are in the readme! We used an asyncified version of dashmap's benchmark suite. The project is in a pretty early stage and I'm sure there are flaws, but I'm pretty happy with the performance. There is some unsafe involved, but we run Miri in ci to (hopefully) catch undefined behavior well before it's in an actual release. We'd appreciate any feedback! Thanks in advance :)
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