Seastar is a C++ server application framework and asynchronous programming library designed for building high-performance, shared-nothing server applications. It functions as a high-performance I/O engine providing direct disk and network access through a shared-nothing framework that partitions data and execution across CPU cores.
The framework distinguishes itself through a thread-per-core architecture that eliminates locking and resource contention by assigning one execution thread to each physical CPU core. It implements a userspace TCP/IP stack and kernel-bypass techniques, integrating with data plane kits to drive network interface cards directly and enable zero-copy networking.
The project covers a broad set of capabilities including asynchronous workflow orchestration via futures and coroutines, cooperative task scheduling with resource isolation, and direct disk I/O using DMA-based APIs. It also provides utilities for TLS network encryption and coordinated graceful service shutdowns.
The project provides containerized build environments and provisioned virtual machines to ensure consistent compilation across different host systems.
