Redis

What is Redis?

Redis is an open-source, in-memory key-value data store known for its speed and flexibility.

Key Features:

• In-Memory Data Store: Redis stores data in RAM, ensuring fast read and write speeds.
• Data Persistence: Unlike other in-memory caches, Redis can persist data to disk.
• Rich Data Structures: Redis is not limited to simple key-value pairs but offers robust structures such as lists, sets, sorted sets, and hashes.
• Pub/Sub Messaging: Redis allows message brokering using Pub/Sub, making it useful for real-time messaging systems.
• Distributed System: Redis supports clustering, enabling horizontal scalability.

Why Redis?

Redis is a popular choice for many reasons:

• High performance: Redis is known for its high performance, which is due to its in-memory data storage and processing capabilities.
• Scalability: Redis is designed to be scalable, which means it can handle a large number of requests and data.
• Flexibility: Redis supports a variety of data structures, which makes it a versatile tool for many different use cases.

Redis Internals: How Does It Work?

Redis is an in-memory data structure server. Let's break down the key components and internals of Redis:

1 Memory Management:

• Redis operates entirely in memory and uses a single-threaded event loop. Data is stored as key-value pairs in RAM, which ensures fast read/write performance.
• Redis leverages a memory-efficient representation called SDS (Simple Dynamic String) to store data.

2 Data Persistence:

Redis can persist data on disk using two primary mechanisms:

• RDB (Redis Database): A point-in-time snapshot mechanism that saves data to disk at specific intervals.
• AOF (Append Only File): Logs every write operation, making it more durable, though at the cost of speed compared to RDB.

3 Eviction Policies:

Since Redis operates in memory, it uses eviction policies to handle data when memory is full:

• LRU (Least Recently Used): Removes the least recently accessed items.
• LFU (Least Frequently Used): Removes items based on access frequency.
• TTL (Time-to-Live): Allows setting expiration times for keys, making it easy to manage short-lived data.

Redis Data Types

Redis supports five data types:

• Strings
• Hashes (Objects)
• Lists
• Sets
• Sorted Sets (Priority Queues)
• Geospatial Indexes