Learning track · 16 concepts
Backend
Production backend strength: HTTP, API design, auth, rate limiting, idempotency, queues, jobs, caching, and observability.
What mastery looks like
This track contains 16 connected concepts rather than an unordered reading list. Mastery means you can move from vocabulary to mechanisms, predict how the system behaves under pressure, and support a design decision with code, measurements, or a failure-recovery exercise. For Backend, use the track description as the boundary: learn enough detail to reason clearly about production backend strength: http, api design, auth, rate limiting, idempotency, queues, jobs, caching, and observability.
A useful explanation names the state involved, the operation that changes it, the resource or safety constraint, and the observable signal that tells you whether the mechanism works. Avoid stopping at product names. Compare at least two approaches, state what each optimizes, and identify what breaks first as scale, concurrency, latency, or uncertainty increases.
Suggested study sequence
Start with HTTP Lifecycle to establish the basic vocabulary. Continue through the core concepts by alternating explanation with an executable drill. Use the related concepts and roadmap milestones to integrate the pieces into a complete system.
At the end of each session, record one decision you can now make, one failure mode you can now predict, and one unanswered question. Revisit that question through the linked primary sources, then prove the answer in the Playground or a real repository. The track is complete when you can transfer the reasoning to an unfamiliar system, not when every page has been opened.
Roadmaps
Concepts in this track
intro
HTTP Lifecycle
DNS → TCP/TLS → request → response: status codes, headers, keep-alive.
core
API Keys
Issuing, hashing, scoping, and rotating keys for machine clients.
core
Rate Limiting
Token bucket, leaky bucket, sliding window.
core
Idempotency
Idempotency keys and dedup windows for safe retries of mutations.
core
Retries & DLQ
Backoff + jitter, poison messages, dead-letter queues.
core
Webhooks
Outbound event delivery: signing, retries, idempotent receivers.
core
Background Jobs
Offloading slow work to workers: scheduling, concurrency, visibility.
core
Caching
Cache-aside, write-through, eviction policies.
core
Message Queues
Kafka, SQS, exactly-once vs at-least-once.
core
Observability
Metrics, logs, traces, context propagation, semantic conventions, sampling, collectors, and telemetry pipelines.
core
API Design
REST, gRPC, versioning, pagination.
core
Auth Systems
OAuth2, JWT, session, RBAC.
core
Payments
Idempotency, sagas, double-entry.
core
Retries & Circuit Breakers
Backoff, jitter, budgets, and breakers — retrying without turning a blip into an outage.
core
Web Security Basics
XSS, CSRF, SQL injection, and CORS — the injection and confused-deputy bugs that keep recurring.
core
Pagination
Offset versus cursor pagination, stable ordering, and why deep pages get expensive.