Faasm is a high-performance stateful serverless runtime. The goal of the project is enabling fast, efficient parallel applications in serverless.

Faasm provides multi-tenant isolation, but also lets functions share regions of memory. These shared memory regions give low-latency concurrent access to data, supporting high-performance distributed serverless applications.

By running WebAssembly, Faasm combines software fault isolation with standard OS tooling to provide security and resource isolation guarantees at low cost. Functions run side-by-side as threads of a single runtime process, with low overheads and fast boot times.

Faasm supports C/C++ natively and extends support to dynamic languages such as Python by compiling the language runtime itself to WebAssembly.

Faasm uses a custom host interface to give functions access to state and interact with the runtime. Larger applications can be constructed by composing multiple functions together dynamically in chains. The Faasm scheduler ensures these functions execute close to their required data, reducing unnecessary duplication and overhead.

Faasm is open-sourced at https://github.com/lsds/Faasm.