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Building Scalable Backend Services in Go

The LRU Cache

Explore how to implement an efficient LRU cache in Go by managing cache entries with a doubly linked list and map. Understand cache operations including adding, removing, moving entries, and how this strategy enhances backend responsiveness by prioritizing frequently accessed data.

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The LRU cache is a popular caching strategy that discards the least recently used items first. This cache eviction policy is based on the assumption that items that have not been accessed recently are less likely to be accessed in the near future. Let us look at how we can implement an LRU cache in Go.

Setup

First, we need to define a data structure that represents a cache entry. The entry should contain the key and value of the cached item. We also need to define a doubly linked list node to manage the order of the entries in the cache.

type LRUCache struct {

	capacity int

	cache    map[int]*CacheEntry

	head     *CacheEntry

	tail     *CacheEntry

}



type CacheEntry struct {

	key   int

	value int

	prev  *CacheEntry

	next  *CacheEntry

}
Data structs for LRUCache

The LRUCache struct contains the following:

  • It contains a capacity field that represents the maximum number of entries that the cache can hold.

  • It contains a size field that represents the current number of entries in the cache.

  • It contains a cache map that maps keys to entries.

  • It contains the head and tail pointers that point to the first and last entries in the doubly linked list.

The CacheEntry struct contains the following:

  • It contains a unique key (key) for every entry. ...