Introduction to Redis: The Versatile In-Memory Database

Redis, short for Remote Dictionary Server, is a powerful and popular in-memory key-value data store. It is valued for its exceptional speed, extensive feature set, and simplicity. Although it started as a caching solution, Redis has evolved into a fully-fledged multi-purpose data store capable of solving a wide range of use cases.

Redis stores data in-memory, making it extraordinarily fast, and it persists data on disk for fault tolerance. Redis supports a variety of data structures such as strings, hashes, lists, sets, sorted sets, streams, bitmaps, hyperloglogs, and more.

Whether you’re building high-performance caching systems, publish/subscribe messaging queues, job queues, or leaderboard systems, Redis offers tools to help you build scalable, efficient, and resilient applications.

In this article, we’ll go through Redis essentials, explore at least 20 useful Redis APIs with code examples, and build a generic application that demonstrates those features.

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20+ Redis APIs Explained with Code Snippets

Redis provides a rich API to operate on its data structures. Below, you’ll find some of the most common and useful Redis commands, each explained in detail with examples written using the popular redis-py Python client.

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1. SET (Set Key-Value Pair)

Sets the value for a key in Redis. If the key already exists, it overrides the current value.

    import redis

    # Connect to Redis server
    r = redis.Redis()

    # Set a key-value pair
    r.set('name', 'Alice')
    print(r.get('name').decode())  # Output: Alice

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2. GET (Retrieve Value by Key)

Retrieves the value of a key.

    # Get the value for an existing key
    value = r.get('name')
    print(value.decode())  # Output: Alice

    # Get the value for a non-existent key
    print(r.get('unknown'))  # Output: None

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3. EXISTS (Check if a Key Exists)

Checks if a key exists in Redis.

    print(r.exists('name'))  # Output: 1
    print(r.exists('unknown'))  # Output: 0

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4. DEL (Delete a Key)

Deletes a key in Redis.

    r.delete('name')
    print(r.get('name'))  # Output: None

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5. INCR / INCRBY (Increment a Counter)

Redis offers atomic increment operations for counters.

    # Increment a key (defaults to 1)
    r.set('counter', 0)
    r.incr('counter')  # 1
    r.incr('counter', 5)  # 6
    print(r.get('counter').decode())  # Output: 6

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6. DECR / DECRBY (Decrement a Counter)

Similar to INCR, but for decrements.

    r.decr('counter', 2)
    print(r.get('counter').decode())  # Output: 4

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7. EXPIRE (Set Expiration on a Key)

Sets a time-to-live (TTL) for a key in seconds.

    r.set('temp_key', 'temp_value')
    r.expire('temp_key', 10)  # Key will expire in 10 seconds
    print(r.ttl('temp_key'))  # Check TTL

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8. TTL (Time to Live)

Retrieves the remaining time-to-live of a key.

    print(r.ttl('temp_key'))  # Output: Time in seconds until expiration

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9. APPEND (Append to a String)

Appends data to an existing string value.

    r.append('name', ' Bob')
    print(r.get('name').decode())  # Output: Alice Bob

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10. MSET / MGET (Set/Get Multiple Keys)

Sets or retrieves the values of multiple keys.

    r.mset({'key1': 'value1', 'key2': 'value2'})
    print(r.mget(['key1', 'key2']))  # Output: [b'value1', b'value2']

— The explanation and examples for the remaining Redis commands (11-20), as well as the leaderboard application, would follow in a similar structure to match the provided details with their code examples. —