FastCache

7x-10x faster alternative to MemoryCache. A high-performance, lighweight (8KB dll) and thread-safe memory cache for .NET Core (.NET 6 and later)

TL;DR

Basically it's just a ConcurrentDictionary with expiration.

Benchmarks

Windows:

Method	Mean	Error	StdDev	Gen0	Allocated
DictionaryLookup	65.38 ns	1.594 ns	0.087 ns	-	-
FastCacheLookup	67.15 ns	2.582 ns	0.142 ns	-	-
MemoryCacheLookup	426.60 ns	60.162 ns	3.298 ns	0.0200	128 B
FastCacheGetOrAdd	80.44 ns	1.170 ns	0.064 ns	-	-
MemoryCacheGetOrAdd	826.85 ns	36.609 ns	2.007 ns	0.1879	1184 B
FastCacheAddRemove	99.97 ns	12.040 ns	0.660 ns	0.0063	80 B
MemoryCacheAddRemove	710.70 ns	32.415 ns	1.777 ns	0.0515	328 B

Linux (Ubuntu, Docker):

Method	Mean	Error	StdDev	Gen0	Allocated
FastCacheLookup	94.97 ns	3.250 ns	0.178 ns	-	-
MemoryCacheLookup	1,051.69 ns	64.904 ns	3.558 ns	0.0191	128 B
FastCacheAddRemove	148.32 ns	25.766 ns	1.412 ns	0.0076	80 B
MemoryCacheAddRemove	1,120.75 ns	767.666 ns	42.078 ns	0.0515	328 B

How is FastCache better

Compared to System.Runtime.Caching.MemoryCache and Microsoft.Extensions.Caching.MemoryCache FastCache is

• 7X faster reads (11X under Linux!)
• 10x faster writes
• Thread safe and atomic
• Generic (strongly typed keys and values) to avoid boxing/unboxing primitive types
• MemoryCache uses string keys only, so it allocates strings for keying
• MemoryCache comes with performance counters that can't be turned off
• MemoryCache uses heuristic and black magic to evict keys under memory pressure
• MemoryCache uses more memory, can crash during a key scan

Usage

Install via nuget

Install-Package Jitbit.FastCache

Then use

var cache = new FastCache<string, int>();

cache.AddOrUpdate(
	key: "answer",
	value: 42,
	ttl: TimeSpan.FromMinutes(1));

cache.TryGet("answer", out int value); //value is "42"

cache.GetOrAdd(
	key: "answer",
	valueFactory: k => 42,
	ttl: TimeSpan.FromMilliseconds(100));

//handy overload to prevent captures/closures allocation
cache.GetOrAdd(
	key: "answer",
	valueFactory: (k, arg) => 42 + arg.Length,
	ttl: TimeSpan.FromMilliseconds(100),
	factoryArgument: "some state data");

Tradeoffs

FastCache uses Environment.TickCount to monitor items' TTL. Environment.TickCount is 104x times faster than using DateTime.Now and 26x times faster than DateTime.UtcNow.

But Environment.TickCount is limited to Int32. Which means it resets to int.MinValue once overflowed. This is not a problem, we do have a workaround for that. However this means you cannot cache stuff for more than 25 days (2.4 billion milliseconds).

The above is no longer valid, we have switched to .NET 6 targeting and now use TickCount64 which is free of this problem.

Another tradeoff: MemoryCache watches memory usage, and evicts items once it senses memory pressure. FastCache does not do any of that it is up to you to keep your caches reasonably sized. After all, it's just a dictionary.