Architecting Redis In-Memory Eviction Strategies (1866)

Technical Overview

Engineering breakdown of Architecting Redis In-Memory Eviction Strategies (1866). Bare-metal hardware performance requires isolated kernel parameters, NUMA-aware memory allocation, and precise eviction policy tuning to meet sub-millisecond SLAs at the edge.

Eviction Policy Taxonomy

• noeviction - Returns errors on memory pressure; suitable for immutable caches.
• allkeys-lru - Evicts least recently used keys across the entire keyspace; ideal for general-purpose caching.
• volatile-lru - Evicts LRU only among keys with an expire set; preserves non-expiring metadata.
• allkeys-lfu / volatile-lfu - Frequency-based eviction; excels when access patterns are skewed.
• allkeys-random / volatile-random - Random eviction; low overhead, unpredictable latency.
• volatile-ttl - Evicts keys with the shortest TTL; useful for time-series rollups.

Edge-Specific Considerations

At the edge, memory footprints are constrained (often < 2 GB per node). Combine maxmemory-policy with maxmemory-samples (default 5) to balance accuracy vs. CPU overhead. For deterministic latency, pin Redis to isolated CPU cores via taskset and disable transparent huge pages (THP).