A **distributed hash table** (DHT) is a decentralized storage system that provides lookup and storage schemes similar to a hash table, storing <u>key-value</u> pairs.

Each node in a DHT is responsible for keys along with the mapped values. Any node can efficiently retrieve the value associated with a given key.

Just like in hash tables, values mapped against keys in a DHT can be any arbitrary form of data.

DHTs have the following properties:

- **Decentralised & Autonomous:** Nodes collectively form the system without any central authority.
- **Fault Tolerant:** System is reliable with lots of nodes joining, leaving, and failing at all times.
- **Scalable:** System should function efficiently with even thousands or millions of nodes.

Just like hash tables, DHTs support the following 2 functions:

1. *put* (key, value)
2. *get* (key)

The nodes in a DHT are connected together through an **overlay network** in which neighboring nodes are connected. This network allows the nodes to find any given key in the key-space.

What is a distributed hash table?

A distributed hash table (DHT) is a scalable, fault-tolerant, decentralized storage system mapping keys to values, allowing efficient data retrieval.