Build Redis (10 scenes)
Scene 09 · Design your Redis deployment
Capstone: pick persistence, HA, and sharding for a stated SLO; the verifier traces each choice back to the scene that taught it.
Previously
You've seen every knob — single thread, encodings, persistence, eviction, TTL, replication, Sentinel, Cluster. Time to assemble them for a real workload, and watch the warning chips light up when your choices contradict each other.
Scene 09
Design your Redis deployment
Diagram
A budget canvas: pick instance count, memory per instance, persistence policy, and replication mode from the controls on the left. The center renders the resulting topology — masters, replicas, sentinels, slot fan-out. The right side lights up warning chips whenever your choices contradict each other (e.g. AOF=always with 200k writes/s, or cluster + multi-key transactions without hash-tag).
Three workloads, three honest configurations. Watch the verifier nod (or refuse) as each SLO drops in and the knobs snap to the deployment that fits it. The captions name the trade — read each one.
Implementation
redis.conf — persistence
fsync policy + RDB snapshot rule
1appendonly yes2appendfsync everysec # ~1s loss on crash3appendfsync always # zero-loss; fsync per write4appendfsync no # OS decides; seconds of loss56save 3600 1 # RDB rule (hour, 1 change)7save 300 100 # RDB rule (5m, 100 changes)8no-appendfsync-on-rewrite no9aof-use-rdb-preamble yes # multi-part AOF (7.0+)1011# stop-writes-on-bgsave-error yes
redis.conf — replication & safety
replica wiring + write-refusal floor
1replicaof <MASTER> 6379 # only on replica nodes2replica-read-only yes34min-replicas-to-write 0 # default: async, best-effort5min-replicas-to-write 1 # refuse writes if <1 in sync6min-replicas-to-write 2 # refuse writes if <2 in sync7min-replicas-max-lag 1089repl-backlog-size 64mb # PSYNC2 partial-resync window10repl-diskless-sync yes1112# masterauth <SECRET>