Systems

Internal building blocks of redis-server. Each subsystem has its own page.

Subsystem	Source	Page
Event loop	src/ae.c, src/ae_*.c, serverCron, beforeSleep	Event loop
Networking	src/networking.c, src/connection.c, src/socket.c, src/unix.c, src/anet.c	Networking
Persistence	src/rdb.c, src/aof.c, src/rio.c, src/chk.c	Persistence
Replication	src/replication.c	Replication
Cluster	src/cluster.c, src/cluster_legacy.c, src/cluster_asm.c, src/cluster_slot_stats.c	Cluster
Scripting	src/eval.c, src/script.c, src/script_lua.c, src/functions.c, src/function_lua.c	Scripting
Modules	src/module.c, src/redismodule.h	Modules
ACL & security	src/acl.c, src/tls.c	ACL & security
Memory management	src/zmalloc.c, src/evict.c, src/expire.c, src/lazyfree.c, src/defrag.c, src/object.c, src/estore.c, src/ebuckets.c	Memory management
IO threads	src/iothread.c, src/eventnotifier.c, src/threads_mngr.c	IO threads
Pub/Sub & client tracking	src/pubsub.c, src/notify.c, src/tracking.c, src/blocked.c, src/timeout.c	Pub/Sub & tracking

These subsystems are not independent libraries; they live in the same address space and share the global server struct. The boundaries are conceptual — the test for whether something belongs in its own subsystem is whether it has its own state machine, its own threads/forks, or its own protocol.

For data-structure primitives (SDS, dict, listpack, rax, …) see Primitives. For user-visible features that span subsystems (data types, transactions, expiration semantics) see Features.