Backend Fundamentals

Language-agnostic backend concepts every developer needs before building web apps.

1. 7.1

   How the web works

   • Client vs server
   • DNS
   • IP & ports
   • TCP
   • What happens when you type a URL
   • How the web works— Clients, servers, DNS, IP addresses, ports and TCP — everything that happens before your code runs.11 min
2. 7.2

   HTTP in depth

   • Requests & responses
   • Methods
   • Status codes
   • Headers & cookies
   • HTTPS / TLS
   • Anatomy of an HTTP request— What a browser actually sends to a server, and what comes back.10 min
   • Headers, cookies and HTTPS— The headers that control content, caching and identity — plus how cookies and HTTPS work.12 min
3. 7.3

   APIs

   • REST principles
   • Resource design
   • Pagination
   • Idempotency
   • GraphQL, gRPC, WebSockets
   • Designing REST APIs— Model resources, choose methods and status codes, and handle pagination, errors and idempotency.13 min
   • Beyond REST: GraphQL, gRPC and WebSockets— Other ways for programs to talk — when each one fits better than REST.10 min
4. 7.4

   Databases

   • Relational vs NoSQL
   • SQL
   • Indexes
   • Transactions & ACID
   • N+1 problem
   • SQL fundamentals— Tables, rows and keys — then querying and changing data with SELECT, INSERT, UPDATE and DELETE.14 min
   • Joins, grouping and subqueries— Combine tables with JOIN, summarize data with GROUP BY, and nest queries.14 min
   • Indexes and transactions— Make queries fast with indexes, and keep data correct with transactions and ACID guarantees.13 min
   • Relational vs NoSQL databases— Document, key-value, wide-column and graph databases — what they're good at and when to choose them.10 min
5. 7.5

   Auth & security

   • AuthN vs AuthZ
   • Sessions vs tokens
   • JWT
   • OAuth 2.0 / OIDC
   • OWASP Top 10
   • Authentication: sessions, tokens and passwords— Prove who a user is, remember them across requests, and store passwords safely.14 min
   • OAuth 2.0 and OpenID Connect— How "Sign in with Google" works, and how apps get limited access to APIs without sharing passwords.12 min
   • Web security essentials— The most common web vulnerabilities and the standard defences every backend developer should apply.13 min
6. 7.6

   Server internals

   • Request lifecycle
   • Middleware
   • Statelessness
   • Config & secrets
   • Logging
   • Inside a backend server— The request lifecycle, middleware, statelessness, configuration, secrets and logging.12 min
7. 7.7

   Performance & scaling

   • Caching
   • CDNs
   • Load balancers
   • Horizontal scaling
   • Rate limiting
   • Caching— Serve repeated reads from memory — cache layers, eviction, expiry and the hard problem of invalidation.13 min
   • Scaling and load balancing— Handle more traffic by scaling up and out, spreading load, and protecting your system with rate limits.13 min
8. 7.8

   Distributed systems

   • Message queues
   • Background jobs
   • Microservices vs monolith
   • CAP theorem
   • Resilience
   • Message queues and background jobs— Move slow work out of the request, decouple services, and process work reliably with queues.12 min
   • Microservices, CAP and resilience— Monoliths vs microservices, the trade-offs of distributed data, and patterns that keep failures contained.14 min
9. 7.9

   Operations

   • Environments
   • Containers
   • CI/CD
   • Monitoring & tracing
   • Health checks
   • Running in production— Environments, containers, CI/CD, health checks and observability — keeping a backend alive.12 min
10. 7.10

    System design basics

    • URL shortener
    • Chat app
    • News feed
    • System design basics— A repeatable approach to designing backend systems — practiced on a URL shortener, a chat app and a news feed.15 min