🧠 Computer Science
Learn how computers think
Systems thinking is as core to growing up sharp as language is. Start with Process Quest or Code Quest, then move on to the system design tools when you're ready for bigger ideas.
Play & learn
Process Quest
A story-driven world map that teaches OS, data structures, digital logic, networks, databases, AI/ML and web tech — one puzzle at a time, from foundations to professional-knowledge-check depth.
Drag & drop
Code Quest
Learn to code the Scratch way — snap real blocks together to move sprites, build games and make things talk. Every lesson checks your actual blocks, not clicks.
📐 System design tools
Calculators and builders for system design interview prep.
QPS & capacity calculator
Back-of-envelope system design estimation
Enter monthly active users, requests per user and payload size to get average/peak QPS, bandwidth, storage (with replication), cache size and server count — the full back-of-envelope estimate for a system design interview. Free.
Open tool →System design diagram builder
Draw components, connect them, pick real tech per box
Drag components (load balancer, cache, database, queue, CDN…) onto a canvas, connect them with arrows, and pick a real technology for each from a curated shortlist. Load a starter example, export as PNG, or copy as Mermaid to paste into your docs. Free.
Open tool →Availability & nines calculator
Chain vs. redundancy math, downtime per year/month/day
Turn "99.95%" into an actual downtime figure, chain component availabilities to find your system's weakest link, and see how many redundant replicas it takes to hit five nines. Free.
Open tool →Sharding & partition calculator
Shard count from data size + write QPS, hash vs. range
Enter total data size, max data per shard, and write QPS to get the shard count your system actually needs — sized by whichever limit hits first. Plus a hash-vs-range-vs-directory partitioning strategy picker. Free.
Open tool →Latency budget calculator
Split a p99 SLA across network, cache, DB and compute hops
Pick a request-path scenario (cache hit, cross-region read, replicated write…), tune each hop's latency, and see exactly where a p99 SLA target is being spent — or blown. Free.
Open tool →Bloom filter sizing calculator
Bit array size, hash count & false-positive rate
Enter item count and target false-positive rate to get the optimal bit array size and hash function count — or flip it around and see the false-positive rate a fixed memory budget gets you. Free.
Open tool →