Multi-tier caching places caches at different levels, each optimized for different access patterns.
Common tiers:
Browser cache: Zero latency, user-specific
CDN: Edge locations, static content
Application cache: Redis/Memcached, shared across servers
Database cache: Query cache, buffer pool
Each tier has different TTLs. Shorter TTLs at higher levels ensure changes propagate. Coordinate invalidation across tiers or accept bounded staleness.