Systa: Learn System Design

Saimum Islam

In-app purchases

About this app

Systa teaches system design the way it actually clicks: by letting you *play* with
the ideas, not just read about them.

Work through bite-sized lessons, then open an interactive simulator and watch how a
load balancer, rate limiter, cache, or queue behaves as you turn up the traffic.
Tweak the algorithm, add servers, trigger failures — and see the trade-offs happen
in real time.

Everything runs offline. No account, no sign-in, no ads, no tracking.

WHAT'S INSIDE
• Interactive simulators (20 and growing) — load balancing, rate limiting, caching,
replication, sharding, queues, CDNs, circuit breakers, and more.
• Structured courses — scaling, storage, networking, AI & LLM systems, and the
fundamentals that tie them together.
• 46 real case studies with design boards — see how well-known systems are built.
• Quizzes, flashcards, and interview prep to lock in what you learn.
• Back-of-the-envelope calculators for QPS, storage, and bandwidth.
• Progress tracking — streaks, levels, and achievements that keep you coming back.

DESIGNED TO READ WELL
A calm, paper-like reading surface with selectable themes, accent colors, serif or
sans body text, and adjustable text size. Light and dark modes included.

FREE & PRO
Foundations is free. A single one-time purchase unlocks everything else — every
course, every simulator, and all case studies. No subscription, ever.

Whether you're prepping for a system design interview or just want to finally
understand how large systems fit together, systa makes it concrete.

What’s new

Update add settings.