Tell about sharding a database to reduce load.

Database sharding is a method of horizontal partitioning of data into multiple parts (shards) to reduce the load on a single server and increase scalability.

Each shard stores a portion of the data, for example, by user key or value range. Requests are directed to the appropriate shard, which reduces the amount of data processed by a single server.

Advantages:

• Reduces load on a single server.
• Improves performance and response speed.
• Allows scaling by adding new shards.

Disadvantages:

• Complexity in implementation and maintenance.
• Difficulties with transactions and data integrity across shards.

Example: if you have a user database, you can shard by the first letter of the last name — all users with last names starting with "A" in one shard, with "B" in another, and so on.