Question 1

What latency numbers and availability targets should every engineer know?

Accepted Answer

**Target Audience:** Beginners — no hardware or operations background assumed.
**Difficulty:** Easy
**Verified with:** Node 22.22 and Python 3.12 (the calculator prints the same output in both).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Every derived number was computed by the example program; the **Verified** section quotes its full output.

## 1. Why This Even Mat

Question 2

How do you approach back-of-the-envelope capacity estimation?

Accepted Answer

**Target Audience:** Beginners to system design — you can multiply and divide; nothing else assumed.
**Difficulty:** Medium
**Verified with:** Node 22.22 and Python 3.12 (the calculator prints the same output in both).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Every number in the worked example was computed by the example program; the **Verified** section quotes its

SYSTEM DESIGNDECODED.

Easy

What latency numbers and availability targets should every engineer know?

Medium

How do you approach back-of-the-envelope capacity estimation?