choosing-a-policy.md

Choosing a Policy

This guide summarizes practical trade-offs and mirrors the benchmark-driven guidance in the latest benchmark guide.

Feature flags: Each policy is gated behind a feature flag (e.g. policy-lru, policy-s3-fifo). Enable only the policies you need for smaller builds. See Compatibility and Features.

Quick Picks

• General purpose, skewed workloads: LRU or S3-FIFO
• Scan-heavy workloads: S3-FIFO or Heap-LFU
• Low latency required: LRU or Clock
• Memory constrained: LRU or Clock
• Frequency-aware: LFU, Heap-LFU, or LRU-K
• Shifting patterns: S3-FIFO or 2Q
• Mixed one-hit + frequent: 2Q or S3-FIFO

Policy Summaries

• LRU: Great default for temporal locality; fast; scan-vulnerable.
• Clock: LRU-like with lower overhead; similar latency to LRU.
• S3-FIFO: Strong scan resistance with low overhead; solid default for mixed workloads.
• LFU / Heap-LFU: Frequency-driven; stable hot sets; slower to adapt.
• LRU-K: Strong scan resistance; more metadata per entry.
• 2Q: Simple scan resistance; needs queue sizing.

Deep Dives

• Implemented policies
• Policy roadmap