Memory overhead

Estimates were performed using Java Agent for Memory Measurements to calculate the runtime size. The size may be affected by compressed references, object padding, etc. applied by the JVM. This benchmark may be run using gradle memoryOverhead which executes MemoryBenchmark.

By forking Java 5's ConcurrentHashMap, Guava has a slight advantage with per-entry optimizations. This is evident when weak and soft reference caching is used. Caffeine must retain additional fields to remove a collected entry due to decorating a Java 8 ConcurrentHashMap.

Caffeine dynamically resizes its internal data structures based on contention. This reduces the initial footprint in favor of using additional memory only as required to meet throughput demands.

Unbounded

Cache	Baseline	Entry
Caffeine	656 bytes	42 bytes
Guava	1,136 bytes	58 bytes

Maximum Size

Cache	Baseline	Entry
Caffeine	552 bytes	74 bytes
Guava	1,560 bytes	74 bytes

Maximum Size & Expire after Access

Cache	Baseline	Entry
Caffeine	584 bytes	82 bytes
Guava	1,560 bytes	74 bytes

Maximum Size & Expire after Write

Cache	Baseline	Entry
Caffeine	616 bytes	90 bytes
Guava	1,728 bytes	90 bytes

Maximum Size & Refresh after Write

Cache	Baseline	Entry
Caffeine	608 bytes	82 bytes
Guava	1,728 bytes	90 bytes

Maximum Weight

Cache	Baseline	Entry
Caffeine	504 bytes	74 bytes
Guava	1,552 bytes	74 bytes

Expire after Access

Cache	Baseline	Entry
Caffeine	560 bytes	82 bytes
Guava	1,560 bytes	74 bytes

Expire after Write

Cache	Baseline	Entry
Caffeine	560 bytes	82 bytes
Guava	1,360 bytes	74 bytes

Expire after Access & after Write

Cache	Baseline	Entry
Caffeine	608 bytes	98 bytes
Guava	1,728 bytes	90 bytes

Weak Keys

Cache	Baseline	Entry
Caffeine	496 bytes	98 bytes
Guava	1,416 bytes	66 bytes

Weak Values

Cache	Baseline	Entry
Caffeine	496 bytes	98 bytes
Guava	1,416 bytes	74 bytes

Weak Keys & Weak Values

Cache	Baseline	Entry
Caffeine	552 bytes	130 bytes
Guava	1,512 bytes	82 bytes

Weak Keys & Soft Values

Cache	Baseline	Entry
Caffeine	552 bytes	146 bytes
Guava	1,584 bytes	90 bytes

Soft Values

Cache	Baseline	Entry
Caffeine	496 bytes	114 bytes
Guava	1,416 bytes	90 bytes