Database sharding

Sharding means splitting your data across multiple nodes. This can be done in different ways:

1. Vertical sharding

• Store tables on different nodes.
• Drawback: If one of these tables gets very large, then you need to re-shard that database.

2. Key-based sharding

• Use part of your data (usually the row ID) to shard it.
• Drawback: The number of nodes is fixed. If you want to add more nodes, then you have to reallocate the data.

3. Directory-based sharding

• Maintain a lookup table for where each data is found.
• Drawback: The lookup table is a single point of failure, that's constantly under load.