Galera is a synchronous multi-master replication middleware for transactional databases, primarily MySQL and MariaDB, implemented as a wsrep provider shared library (libgalera_smm.so). The codebase provides total-order multicast group communication via a layered protocol stack (GCS/gcomm), conflict detection through certification of write-sets, incremental state transfer (IST) with a multi-tier cache (gcache), and an arbitrator daemon (garbd) for quorum maintenance. Architecturally, it is structured as a set of cooperating C++ libraries: galerautils (memory allocators, configuration, threading, hashing), gcs (group communication service with membership and flow control), gcomm (transport abstraction with EVS/PC/GMCast protocols), galera (replication engine with certification and write-set handling), and gcache (write-set caching in memory, ring buffer, and memory-mapped pages). The code is well-tested with unit tests (Check framework), regression tests, and integration test scripts. While the core replication logic and utility libraries are well-crafted and modular, the project bundles an older version of the ASIO networking library and retains C++03 compatibility shims, contributing to moderate technical drift. The repository is actively maintained with regular commits and issue triage.