LRU Memory Cache Library in Rust

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in-memory-cache is a straightforward, yet powerful crate that delivers an easy-to-use in-memory cache solution with a Least Recently Used (LRU) eviction policy. This crate facilitates the efficient storage of key-value pairs, providing automatic eviction of the least recently accessed entries when the cache reaches its predefined capacity.


  • Easy-to-use API for adding and retrieving items from the cache.
  • Supports two types of limits: capacity and size.
  • Supports limiting cache size based on the number of entries or the total size in bytes.
  • Evicts the oldest entries when the cache reaches its limit.
  • Error handling for content that exceeds the cache's size limit.


To use the in-memory-cache crate, add the following dependency to your Cargo.toml file:

version = "0.4"
git = ""


Here is an example demonstrating how to use the in-memory-cache crate:

use in_memory_cache::{Cache, Entry};

fn main() {
    // Create a cache with a capacity of 5 items
    let mut cache = Cache::with_capacity(5);

    // Add entries to the cache
    cache.add("key1", "value1").unwrap();
    cache.add("key2", "value2").unwrap();
    cache.add("key3", "value3").unwrap();
    cache.add("key4", "value4").unwrap();
    cache.add("key5", "value5").unwrap();

    // Retrieve an entry from the cache
    if let Some(entry) = cache.get("key1") {
        println!("Entry found: {:?}", entry);

    // Add a new entry, evicting the oldest entry from the cache
    cache.add("key6", "value6").unwrap();

    // Clear the cache

In this example, we create a cache with a capacity of 5 items using Cache::with_capacity(). We use the add() method to add entries to the cache, and the get() method to retrieve entries from the cache.

If the cache reaches its capacity, the oldest entry will be evicted when a new entry is added. The clear() method can be used to remove all entries from the cache.

Further customization

The Cache struct provides additional methods to create a cache with a size-based limit and methods to retrieve entries as bytes::Bytes. You can choose the appropriate method based on your specific use case.

Error Handling

The add() method returns a Result<(), Box<dyn std::error::Error>>, allowing you to handle errors that occur when adding entries to the cache. If the content exceeds the cache's size limit, an Error will be returned.


This crate is licensed under the MIT License. Please refer to the LICENSE file for detailed licensing information.