System Design: The Key-value Store

Let's understand the basics of designing a key-value store.

We'll cover the following

Introduction to key-value stores

Key-value stores are distributed hash tables (DHTs)A distributed hash table (DHT) is a decentralized storage system that provides lookup and storage schemes similar to a hash table, storing key-value pairs. Source: https://www.educative.io/edpresso/what-is-a-distributed-hash-table. A key is generated by the hash function and should be unique. In a key-value store, a key binds to a specific value and doesn’t assume anything about the structure of the value. A value can be a blob, image, server name, or anything the user wants to store against a unique key.

Usually, it’s preferred to keep the size of value relatively smaller (KB to MB). We can put large data in the blob store and put links to that data in the value field. Key-value stores are useful in many situations, such as storing user sessions in a web application and building NoSQL databases.