Tell me about database sharding.

Database sharding is a method of horizontal scaling where data is partitioned into parts (shards), each stored on a separate server or cluster. This allows distributing the load and increasing the system's performance and capacity.

Key points:

• Horizontal partitioning: data is divided by a key (e.g., user ID) into multiple databases.
• Scalability enhancement: each shard handles only its part of the data, reducing the load.
• Challenges: requires a routing mechanism to direct queries to the correct shard, and it is more complex to ensure transactions and data integrity.

Example: if you have a user table with millions of records, you can split it into 10 shards based on ID ranges, so queries for different users are processed in parallel on different servers.