gleam

Uses pure Go mappers and reducers with concurrency, and merges multiple map-reduce steps for better performance, as stated in the README.

Executors run in separate OS processes to avoid GC issues, with automatic memory adjustment based on data size hints, keeping memory usage low (about 10 MB per agent).

Supports standalone or distributed runs, with adjustable in-memory or on-disk modes for streaming and back pressure, enabling fault tolerance via OnDisk persistence.

The Go codebase is simpler than Scala/Java/C++, allowing developers to easily write custom functions and plugins, as highlighted in the philosophy section.