Caching systems are usually in-memory key-value databases that provide very fast access to data. They sit between your application and the database.

Depending on your use case, you can either cache only the results of the database queries, or cache the entire response objec...

Systems can be scaled:

• Vertically - by increasing the resources of a specific node (more CPU, memory, disk etc.). This is easier to do, but it's limited. You can only add so many CPU cores and memory.
• Horizontally - by adding more nodes of the ...

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 datab...

Slow operations should be done asynchronously to avoid making users wait for long periods of time until their requests are processed.

Sometimes this can be done in advance, by pre-processing data that you know users will need. For example, a forum might per...