Capacity Estimator — Interactive System Design Lab

Select a system archetype (social feed, video platform, chat, file storage), adjust daily active users, requests per user, and data sizes, then watch the capacity numbers recalculate in real time. Build intuition for what 10M users actually means at the infrastructure level — and why the read/write ratio determines your architecture more than the raw user count.

Dial up users and request patterns — watch QPS, storage, and bandwidth derive themselves.

This free interactive simulation runs directly in your browser — no account needed. Adjust the parameters and watch how the system responds in real time.

Concepts covered

• back of envelope
• capacity planning
• QPS
• storage estimation
• bandwidth
• system design math

Read the guide

• Back-of-Envelope Estimation — Before you touch architecture, you need numbers. Learn the mental math that turns vague requirements into concrete scale targets — the skill interviewers test before everything else.
• Latency vs Throughput — Latency is how fast a car travels. Throughput is how many cars pass the toll booth. If you confuse them, you'll optimize the wrong thing.