Depending on the type of system you are designing, you need to estimate its scale: how many users will access it every day, how much data you will store and process, etc.

You should be careful when making assumptions. Incorrect assumptions can dramatically change th...

You can't design a system if you don't know what you're designing.

First, ask questions to clarify what you need to implement. Then make a list of all major features and use cases that your design must cover.

For example, if you're designing TinyURL, that list mig...

Once you have a basic design in mind, focus on the key issues. Identify the bottlenecks and major challenges of the system, and then adjust your design to handle them.

In the TinyURL example, a challenge you might consider is that some URLs are frequently accessed, whil...