Redis Explained: Why Developers Keep Putting It in Their Stack

Redis is often described as an in-memory database, but its usefulness goes far beyond simply storing key-value pairs.

It is commonly used for:

Traditional databases usually need to access persistent storage.

Redis primarily operates in memory.

For example:

await redis.set("user:123", JSON.stringify(user));

Later:

const user = await redis.get("user:123");

Because the data is stored in memory, operations can be extremely fast.

Suppose your application repeatedly requests a product:

GET /products/123

Without caching:

Application → Database → Application → User

With caching:

Application → Redis
                ↓
              Cache Hit

The database doesn't need to process every request.

Cached data should often expire.

await redis.set(
  "product:123",
  JSON.stringify(product),
  { EX: 300 }
);

This stores the value for five minutes.

Expiration prevents stale data from remaining indefinitely.

Imagine an API allowing 100 requests per minute.

Redis can track request counts:

rate-limit:user123 = 87

Once the count exceeds the limit, the application can reject additional requests.

Redis shouldn't automatically replace your primary database.

A relational or document database is usually responsible for durable application data.

Redis is often better suited for fast, temporary, or coordination-related data.

Redis is valuable because it solves several performance and distributed-system problems with a relatively simple interface.

Learning Redis is especially useful for backend developers working on production systems.