Backend
Servers, data & large-scale system design. · 11 notebooks
System Design
A complete, story-driven System Design course — every concept grounded in how real companies (Netflix, Uber, WhatsApp, Amazon, Twitter…) actually build at scale, with hand-drawn diagrams and worked interview questions.
Open notebookDatabases 101
Hand-written notes on the essentials of databases — SQL vs NoSQL, ACID transactions and indexing.
Open notebookDatabase Design
The complete craft of database design — from a blank page to the schemas behind LinkedIn, Spotify, WhatsApp, Zoom and Zomato. Covers requirements, ER & EER modeling, keys & constraints, normalization (1NF→BCNF→5NF), indexing, partitioning, transactions & isolation, SQL vs NoSQL, OLTP vs OLAP, and real-world designs — all with hand-drawn diagrams and worked exercises.
Open notebookREST API Design
How the best APIs in the world are actually built. A hands-on, diagram-rich walk through HTTP, REST constraints, resource & URI design, methods & status codes, idempotency, pagination, errors, versioning, auth, rate limiting, caching, webhooks and security — every idea grounded in how Stripe, GitHub, Twilio, Slack and Google design their public APIs, with worked exercises.
Open notebookAuthentication & Authorization
How real systems prove who you are and decide what you can do. A hands-on, diagram-rich walk through credentials & MFA, password hashing, sessions vs JWTs, OAuth 2.0 & OpenID Connect, RBAC/ABAC/ReBAC, SSO & SAML, the classic attacks (CSRF, XSS, token theft) and their defenses, and the passwordless future — all grounded in how Google, AWS Cognito, Auth0, Okta and passkeys actually work.
Open notebookRedis & Caching Strategies
How to make systems fast with caching — and how Redis powers it. A hands-on, diagram-rich walk through caching patterns (cache-aside, write-through, write-behind), TTL & eviction, the invalidation problem, Redis data structures, distributed locks, rate limiting, leaderboards, pub/sub & streams, persistence, replication & clustering, and the failure modes that bite at scale — all grounded in how Twitter, Instagram, Facebook, Netflix and Stack Overflow actually cache.
Open notebookSQL Mastery
Go from SELECT to sub-second analytics queries. A hands-on, diagram-rich, code-first walk through the logical query pipeline, joins, aggregation, subqueries, CTEs & recursion, window functions, transactions & isolation, indexing for query writers, reading EXPLAIN plans, and the anti-patterns that make queries crawl — plus the real analytics patterns (cohorts, funnels, warehouses, dbt) that companies like Airbnb, Netflix and Uber run every day.
Open notebookMicroservices Architecture
How to build systems as fleets of small, independently deployable services — and when you shouldn't. A hands-on, diagram-rich walk through service boundaries & DDD, database-per-service, sync vs async communication, API gateways, service discovery & mesh, sagas/event-sourcing/CQRS/outbox for distributed data, resilience patterns (circuit breakers, retries, observability), delivery (containers, canary deploys, contract testing), the classic anti-patterns and the strangler-fig migration — grounded in how Netflix, Amazon, Uber, Segment and Shopify actually built (and sometimes un-built) microservices.
Open notebookDesign Patterns & SOLID
Write code that other engineers (and future-you) can actually maintain. A hands-on, diagram-rich, code-first walk through coupling & cohesion, the five SOLID principles, and the Gang of Four patterns — Factory, Builder, Singleton, Adapter, Decorator, Facade, Proxy, Composite, Strategy, Observer, Command, Template Method, State and more — plus over-engineering anti-patterns and the patterns hiding inside Spring, NestJS, React and the Java standard library. Every idea shown with real TypeScript and industry examples.
Open notebookMessage Queues & Event-Driven Architecture
How modern systems stay fast, decoupled and resilient by talking through messages instead of blocking calls. A hands-on, diagram-rich walk through message brokers, queues vs pub/sub, the messaging patterns, delivery guarantees & idempotency, ordering, dead-letter queues & backpressure, and event-driven architecture (event types, sagas, CQRS, the outbox pattern, schema evolution) — plus a RabbitMQ-vs-Kafka-vs-SQS tour, grounded in how LinkedIn, Uber, Netflix and Amazon actually build event-driven systems.
Open notebookApache Kafka
A complete Apache Kafka course — concepts AND hands-on. From topics, partitions & exactly-once delivery to coding the Producer/Consumer APIs, offset management, rebalancing and custom serializers, grounded in how real companies stream events at scale.
Open notebook