RethinkDB is an open-source, distributed, NoSQL database designed for real-time applications. It stores JSON documents and supports automatic failover, sharding, and replication. The system exposes a powerful query language (ReQL) with support for joins, aggregations, geospatial queries, and real-time change feeds. The architecture is built on a custom coroutine runtime for efficient concurrency, a log-structured storage engine with B-tree indexes, and a peer-to-peer clustering layer using Raft consensus for metadata management. External dependencies include OpenSSL, Protobuf, jemalloc, zlib, and QuickJS for JavaScript execution. The codebase demonstrates strong engineering in distributed systems, but is now stale with limited active maintenance and significant technical debt from outdated C++ practices and vendored third-party libraries.