It is also called Capacity Estimation or Guesstimate – this is where you quickly calculate the expected load, storage, bandwidth, etc., to guide your system's design decisions.
Why Use It?
- To understand the scale of the system
- To choose between tech options (e.g., SQL vs NoSQL, cache vs DB, etc.)
- To know how many servers or storage units you will need
- To impress interviewers by thinking practically and scaling wisely
Basic Format
In interviews, say:
Let me quickly do some back-of-the-envelope estimations to figure out the scale.
Then go through:
- Users and traffic
- Data size and growth
- Bandwidth
- Read/Write ratio
- Latency/SLA (if needed)