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 the MemoryBenchmark.

By forking Java 5's ConcurrentHashMap, Guava has a slight advantage with per-entry optimizations. This is especially 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 may lazily initialize or dynamically resize its internal data structures based on usage. This reduces the footprint in favor of using additional memory only as required to meet usage demands (e.g. throughput).

Unbounded

Cache	Baseline	Entry
Caffeine	264 bytes	54 bytes (56 aligned)
Guava	1,032 bytes	58 bytes (64 aligned)

Maximum Size

Cache	Baseline	Entry
Caffeine	1,112 bytes	74 bytes (80 aligned)
Guava	1,384 bytes	74 bytes (80 aligned)

Maximum Size & Expire after Access

Cache	Baseline	Entry
Caffeine	1,152 bytes	82 bytes (88 aligned)
Guava	1,384 bytes	74 bytes (80 aligned)

Maximum Size & Expire after Write

Cache	Baseline	Entry
Caffeine	1,176 bytes	90 bytes (96 aligned)
Guava	1,544 bytes	90 bytes (96 aligned)

Maximum Size & Refresh after Write

Cache	Baseline	Entry
Caffeine	1,168 bytes	90 bytes (96 aligned)
Guava	27,200 bytes (?)	90 bytes (96 aligned)

Maximum Weight

Cache	Baseline	Entry
Caffeine	1,120 bytes	82 bytes (88 aligned)
Guava	1,376 bytes	74 bytes (80 aligned)

Expire after Access

Cache	Baseline	Entry
Caffeine	1,008 bytes	82 bytes (88 aligned)
Guava	1,384 bytes	74 bytes (80 aligned)

Expire after Write

Cache	Baseline	Entry
Caffeine	1,008 bytes	82 bytes (88 aligned)
Guava	1,192 bytes	74 bytes (80 aligned)

Expire after Access & after Write

Cache	Baseline	Entry
Caffeine	1,048 bytes	98 bytes (104 aligned)
Guava	1,544 bytes	90 bytes (96 aligned)

Weak Keys

Cache	Baseline	Entry
Caffeine	560 bytes	98 bytes (104 aligned)
Guava	1,240 bytes	66 bytes (72 aligned)

Weak Values

Cache	Baseline	Entry
Caffeine	560 bytes	98 bytes (104 aligned)
Guava	1,240 bytes	74 bytes (80 aligned)

Weak Keys & Weak Values

Cache	Baseline	Entry
Caffeine	616 bytes	130 bytes (136 aligned)
Guava	1,416 bytes	82 bytes (88 aligned)

Weak Keys & Soft Values

Cache	Baseline	Entry
Caffeine	616 bytes	146 bytes (152 aligned)
Guava	1,416 bytes	98 bytes (104 aligned)

Soft Values

Cache	Baseline	Entry
Caffeine	560 bytes	114 bytes (120 aligned)
Guava	1,240 bytes	90 bytes (96 aligned)