Seastar

Seastar is a C++ framework built by Avi Kivity's team at ScyllaDB that proved the thread-per-core model at scale: pin one thread per physical core, give each thread its own memory allocator, network queue, and storage partition, and communicate only through explicit message passing. ScyllaDB claims near-linear scaling — doubling cores doubles throughput — because there is essentially no Amdahl's Law serial bottleneck from inter-core coordination.

glommio is Seastar's direct spiritual successor in Rust, designed by Glauber Costa after seven years building ScyllaDB. ByteDance independently arrived at the same conclusions when building monoio for their proxy infrastructure.

Seastar's own concurrency model — futures, continuations, sharded executors — was the design that informed P2300 and ultimately C++26 senders-receivers. The standard's value-flow asynchronous model is essentially Seastar's continuation-style futures refined into a scheduler-agnostic algebra. Where Seastar baked in its own scheduler, std::execution makes the scheduler a parameter — but the structural lineage from Seastar through libunifex to P2300 is direct.