Async Connection Pool

A bounded async connection pool built in Rust with a guard pattern — because managing shared resources safely across concurrent tasks is one of those problems that looks simple until it isn't.

The idea is straightforward: you have a fixed number of connections and many tasks competing for them. When a task gets a connection it holds it exclusively, does its work, and the connection automatically returns to the pool when it goes out of scope. No manual release, no forgotten returns, no leaks — Rust's Drop trait handles it.

What made this interesting to build is that the same pattern shows up directly in ML inference systems. GPU KV cache slots work exactly like connections in a pool — fixed capacity, multiple requests competing for slots, slots must be released after each request completes. Building this in Rust made that mental model concrete.

What it covers

• Semaphore for bounding concurrent access
• RAII guard pattern with Deref and Drop
• Why std::sync::Mutex and not tokio::sync::Mutex — Drop is synchronous and cannot .await
• Arc for shared ownership across async tasks

Run it

cargo test