SeniorPath

SeniorPath helps software engineers with 2 to 3 years of experience grow into senior engineers and architects. It explains how real systems are built, how they break, and how teams fix them, in simple English.

Every lesson has the same eight parts: a real incident or story, the idea in plain words, a step-by-step diagram, the trade-offs, how it works at scale, how to use AI tools on it, a short quiz, and sources to go deeper.

WHAT YOU GET
• 74 full lessons on a map of 225 topics, with more lessons in each update. Tracks: foundations, data, distributed systems, building at scale, reliability and security, domains like payments, e-commerce, SaaS and games, the senior engineer's craft, and AI-native engineering.
• Step-through diagrams. Go one step at a time, swipe, pinch to zoom, and share a step as a picture.
• Six interactive animations: a cache stampede, replication lag, a staged rollout, a token bucket, a hash ring and a Raft election. Move the sliders and see what happens.
• Real incidents and case studies from companies' own postmortems and engineering blogs, with a link to each.
• A glossary built into the text. Tap any underlined term to see what it means.
• Learning paths that put the lessons in a good order, with your next lesson always one tap away.
• Search across lessons, terms, incidents and case studies.

MADE TO RESPECT YOU
• Everything works offline. The app has no internet permission.
• No account, no ads, no tracking. Your progress stays on your phone.
• Move your progress between the app and the website (seniorpath.dev) with one small file.
• Light and dark themes, large text, and screen reader support.

Every lesson is checked against its sources, and every claim links to where it came from. Spotted a mistake? "Report a mistake" at the end of each lesson opens a short form.

The lessons and diagrams are free to share under Creative Commons BY-NC-SA 4.0. The app's code is open source (MIT).

10 new lessons: OS essentials, data models, requirements and non-functional needs, reconciliation, prompt and context engineering, fan-out on write vs read, design deep dives, mechanical sympathy, stream processing, and complexity and deep modules. 65 new glossary terms.