
ActiveJ
Our Open Source Foundation
At the base of our stack is ActiveJ, the high-performance asynchronous Java framework we develop and maintain as open source. It is a ground-up rethinking of how Java systems should handle I/O, serialization, codegen, and async workflows when every microsecond and allocation matters.
We built ActiveJ after evaluating mainstream frameworks that could not meet our latency and throughput requirements at ad tech scale. Open-sourcing it makes this infrastructure available to teams who need the same performance profile in production.
- Virtual-thread-first asynchronous I/O for readable, sequential code at extreme concurrency.
- Runtime bytecode generation for zero-overhead serialization that competes with hand-written code.
- Byte buffer pooling and vectorized I/O to preserve throughput from network to storage.
- Minimal-allocation hot paths that keep GC pressure low under sustained heavy traffic.
Explore technical documentation at activej.io.



