15entries
Concepts
Short, practical explanations of the ideas backend engineers rely on every day.
- Authentication
- Networking
- Databases
- Caching
- Distributed Systems
- Architecture
- Security
- Scalability
Clear concepts.Scalable systems.Smarter with AI.
Notes on software concepts, system design practices, and AI — written from real engineering experience, for engineers who want to understand how things work.
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- System Designs
- 66
- Engineering Practices
- 8
- AI Notes
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Everything on this site belongs to one of three tracks. Start wherever your current problem is.
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System Design
Design scalable, reliable and efficient systems.
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Explore AI concepts, tools and real-world applications.
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Featured system designs
Full walkthroughs — requirements, capacity, architecture and the trade-offs behind each decision.
Scalability
500K requests/sec gateway-wide, 100K unique clients
Designing a Rate Limiter
Design a distributed rate limiter for an API gateway: algorithm choice, distributed counters, and protecting shared backends under load.
Real-time
50M DAU, 2M concurrent connections, 15B messages/day
Designing a Chat System
Design a real-time chat system like WhatsApp or Slack: connection management, message ordering, delivery guarantees, and fan-out at scale.
Messaging
10M notifications/day, 350 QPS peak
Designing a Notification System
Design a scalable notification system supporting email, SMS and push, with fan-out, retries, and per-channel rate limits.
Storage
100M new URLs/month, 8K redirects/sec peak
Designing a URL Shortener
Design a URL shortening service like Bitly: encoding schemes, redirect latency, and read-heavy caching at scale.
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Why this exists
If I cannot explain it clearly, I have not understood it well enough yet. That is the whole editorial policy — write it down, find the gap, rewrite it.
28 entries so far, across 16 categories. Nothing here is sponsored, generated in bulk, or padded for length — if a page is short, it is because the idea is short.