Memcached vs etcd: What are the differences?

Introduction

In this article, we will discuss the key differences between Memcached and etcd. Memcached is an in-memory caching system, while etcd is a distributed key-value store. Both have their own unique features and use cases. Let's explore their differences in detail.

1. Data Persistence: Memcached does not support data persistence, which means that if the server restarts or crashes, all the cached data will be lost. On the other hand, etcd provides built-in data persistence, ensuring that the data remains intact even after a restart or failure.

2. Consistency and Consensus: Memcached does not provide strong consistency guarantees. It uses a simple hashing algorithm to distribute data among multiple servers, but there is no consensus mechanism. In contrast, etcd uses the Raft consensus algorithm to achieve strong consistency across the distributed key-value store.

3. Distributed Transactions: Memcached does not support distributed transactions, making it unsuitable for scenarios that require atomicity across multiple operations. Etcd, on the other hand, provides support for distributed transactions, allowing multiple operations to be grouped together and executed atomically.

4. Watch and Notification Mechanism: Memcached does not provide a built-in mechanism for clients to watch changes to the data. In contrast, etcd offers a watch feature that allows clients to be notified of changes to the stored data, enabling reactive programming and event-driven architectures.

5. Advanced Querying and Indexing: Memcached is a simple key-value store and does not provide advanced querying capabilities or indexing support. Etcd, on the other hand, allows the use of range queries, prefixes, and even user-defined indexes, making it more suitable for scenarios that require complex querying operations.

6. Configuration Management: While both Memcached and etcd can be used for configuration management, etcd provides additional features such as distributed locks and leader election, making it more suitable for managing the configuration of distributed systems.

In summary, Memcached is a lightweight and fast in-memory caching system without data persistence and advanced querying capabilities, while etcd is a distributed key-value store with data persistence, strong consistency, support for distributed transactions, advanced querying capabilities, and additional features for configuration management.