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16-Week Backend SDE-II Preparation Roadmap (Node.js / TypeScript)

Goal of this file: Give you a phase-wise roadmap (8, 12, 16-week options) that coordinates JS/TS, Node.js, DBs, Redis/queues, system design, machine coding, DSA, and theory.

Roadmap Overview​

  • Phase 1 (Weeks 1–3): JavaScript & TypeScript Deep Dive
  • Phase 2 (Weeks 4–5): Node.js Backend Engineering
  • Phase 3 (Weeks 6–7): Databases – MongoDB + MySQL
  • Phase 4 (Week 8): Redis + Queues
  • Phase 5 (Weeks 9–11): System Design (HLD + LLD)
  • Phase 6 (Weeks 12–13): Machine Coding Rounds
  • Phase 7 (Weeks 14–15): DSA for Backend Interviews
  • Phase 8 (Week 16): Theory, Infra, AWS, and Revision

Parallel tracks throughout:

  • DSA: 3–5 problems/day (focused set).
  • Theory: short daily/alternate-day sessions.
  • Projects: 1–2 substantial backend projects across the 16 weeks.

Timeline Options​

TrackRecommended ForHow to Use This Roadmap
16-weekYou want deep mastery + side projectsFollow phases exactly as mapped to week-01 to week-16
12-weekYou have prior backend experienceMerge some phases (TS+Node, DB+Redis, DSA+Theory)
8-weekYou are experienced and just polishingTake core topics only and aggressively compress

12-Week Compression Hint​

  • Combine:
    • Phase 1 + Phase 2 → 4 weeks total
    • Phase 3 + Phase 4 → 3 weeks total
    • Phase 5 → 3 weeks
    • Phase 6 + Phase 7 + Phase 8 → 2 weeks (intense revision)

8-Week Compression Hint​

  • Phase 1 + 2 → 2 weeks
  • Phase 3 + 4 → 1.5 weeks
  • Phase 5 → 2 weeks
  • Phase 6 + 7 + 8 → 2.5 weeks (heavy practice + revision)

Use week-XX.md files to pick which days to drop/merge.

Phase 1 (Weeks 1–3): JavaScript & TypeScript Deep Dive​

Focus: Build a rock-solid foundation in JS/TS so Node.js + system design become easier.

  • Key Topics

    • JS Internals
      • Memory model, call stack, heap.
      • Event loop internals, macrotasks vs microtasks.
      • Closures, lexical scope, this, prototype chain, inheritance.
    • TS Essentials
      • Types, interfaces, enums, generics.
      • Union, intersection, literal types.
    • TS Advanced
      • Utility types (Partial, Pick, Omit, Record, Readonly, etc.).
      • Discriminated unions, type narrowing.
      • Conditional types (high-level understanding).
    • Async Patterns
      • Promises, async/await, error handling.
      • Streams (readable/writable/transform), backpressure.

  • Outcomes by End of Phase

    • You can read and write modern TypeScript confidently.
    • You understand why async bugs happen and can debug them.
    • You can explain the event loop with a simple diagram.

Cross-links

  • Day-wise plan: week-01.md, week-02.md, week-03.md.
  • DSA: start with arrays/strings/hash maps (see dsa-backend-plan.md).

Phase 2 (Weeks 4–5): Node.js Backend Engineering​

Focus: Build real, production-like backend services with Node.js and TypeScript.

  • Key Topics

    • Node Internals
      • Process model, event loop in Node context, libuv basics.
      • Clustering, worker threads (overview), multi-process patterns.
    • API Development
      • Express vs Fastify: design choices and trade-offs.
      • Routing, controllers, services, repository layers.
      • Middleware architecture and error handling.
    • Auth & Security
      • JWT vs sessions, refresh tokens, OAuth2 basics.
      • OWASP basics: input validation, SQL/NoSQL injection, XSS, CSRF.
      • Rate limiting, IP blocking, and API keys.
    • File Handling & Streams
      • Handling uploads/downloads, streaming large files.
    • Logging & Monitoring
      • Structured logs, correlation IDs, log levels.
      • Basic metrics (latency, throughput, error rate).

  • Outcomes by End of Phase

    • You can build a multi-route REST API with good structure.
    • You can add auth, validation, error handling, and logging.
    • You know how to profile basic performance issues.

Cross-links

  • Day-wise plan: week-04.md, week-05.md.
  • Machine coding: start simple problems (see machine-coding-bank.md).

Phase 3 (Weeks 6–7): Databases (MongoDB + MySQL)​

Focus: Design schemas, optimize queries, and understand trade-offs.

  • Key Topics

    • Data Modeling
      • Normalization (1NF, 2NF, 3NF) vs denormalization.
      • One-to-many, many-to-many, polymorphic associations.
    • Indexes & Query Plans
      • B-tree indexes, composite indexes, covering indexes.
      • EXPLAIN (MySQL), query planner basics.
    • Transactions
      • MySQL: ACID, isolation levels, locks.
      • MongoDB: multi-document transactions (when & why).
    • ORM/ODM vs Raw
      • Mongoose vs raw MongoDB driver: pros/cons.
      • MySQL drivers, query builders.
    • N+1 Problems
      • How N+1 occurs (ORM & manual queries).
      • Techniques: joins, batching, preloading, caching.
    • Caching & Replication Basics
      • Read replicas, primary/secondary.
      • Simple caching strategies for hot reads.

  • Outcomes by End of Phase

    • You can design schemas for typical web apps.
    • You can read query plans and optimize slow queries.
    • You understand ACID vs CAP at a practical level.

Cross-links

  • Day-wise plan: week-06.md, week-07.md.
  • Projects: start DB-heavy parts (see projects.md).

Phase 4 (Week 8): Redis + Queues​

Focus: Understand caching, rate limiting, and background processing.

  • Key Topics

    • Redis Fundamentals
      • Strings, lists, sets, sorted sets, hashes, TTL.
      • Eviction policies, persistence (RDB/AOF).
    • Caching Strategies
      • Cache-aside, write-through, write-back.
      • Dealing with cache stampedes, thundering herds.
    • Rate Limiting
      • Token bucket, leaky bucket, sliding window counters.
      • Implementing with Redis (Lua scripts or primitives).
    • Queues
      • BullMQ (Redis-based), RabbitMQ, SQS overview.
      • Producer/consumer patterns.
      • Dead-letter queues, retries, backoff strategies.
    • Job Scheduling
      • Delayed jobs, CRON-like scheduling.

  • Outcomes by End of Phase

    • You can build a rate limiter and basic cache.
    • You can design and implement a job processing pipeline.

Cross-links

  • Day-wise plan: week-08.md.
  • Machine coding: rate limiter, pub/sub, job queue problems.

Phase 5 (Weeks 9–11): System Design (HLD + LLD)​

Focus: Design complete systems, not just endpoints.

  • Key Topics (HLD)

    • Scalable REST APIs
      • API gateway, service boundaries, versioning.
      • Pagination, filtering, idempotency.
    • Real Systems
      • Uber/Swiggy: location, matching, pricing, surge, driver status.
      • Instagram: media storage, feed generation, notifications.
      • Notification system: fanout, retries, multi-channel.
      • Auth service: token management, sessions, SSO basics.
      • Rate limiter service: global vs per-service/per-endpoint.
      • File storage service: S3, CDN, presigned URLs.
      • Log processing pipeline: ingestion, buffering, storage, search.

  • Key Topics (LLD)

    • Class diagrams, interfaces, layering.
    • SOLID principles and patterns (Factory, Strategy, Adapter, Observer, Repository).
    • Clean boundaries: controller/service/repository/domain.

  • Outcomes by End of Phase

    • You can explain and draw system designs with trade-offs.
    • You can propose LLD for core components with patterns.

Cross-links

  • Day-wise plan: week-09.md, week-10.md, week-11.md.
  • Reference systems: projects.md.

Phase 6 (Weeks 12–13): Machine Coding Rounds​

Focus: Implement well-designed solutions quickly under interview constraints.

  • Key Topics

    • Translating requirements → APIs/classes/data models.
    • Making assumptions explicit, clarifying constraints.
    • Writing clean, modular, testable Node.js/TS code.
    • Applying patterns & SOLID.

  • Core Problems (see machine-coding-bank.md for full specs)

    • Parking lot, Splitwise, Rate limiter, Cache implementation.
    • In-memory DB, Pub/sub system, Notification service.
    • URL shortener, Task scheduler, Feature flag system, etc.

  • Outcomes by End of Phase

    • You can complete 1–2 machine coding problems in 60–90 minutes each.
    • You have a portfolio of small, well-structured codebases.

Cross-links

  • Day-wise plan: week-12.md, week-13.md.

Phase 7 (Weeks 14–15): DSA for Backend Interviews​

Focus: Targeted practice on backend-relevant problems.

  • Key Topics

    • Arrays, strings, hash maps, sets.
    • Trees, graphs (BFS/DFS, shortest path, topological sort).
    • Two pointers, sliding window.
    • Heaps/priority queues.

  • Plan

    • Solve 3–5 problems per day.
    • Rotate topics: arrays/strings → sliding window → trees → graphs → heaps.
    • Revisit earlier mistakes and write a "patterns" cheat sheet.

  • Outcomes by End of Phase

    • You can solve medium-level problems consistently.
    • You have a repertoire of patterns to apply rapidly.

Cross-links

  • Day-wise plan: week-14.md, week-15.md.
  • Topic details: dsa-backend-plan.md.

Phase 8 (Week 16): Theory, Infra, AWS, and Final Revision​

Focus: Tie everything together, polish weak areas, and prepare for interviews.

  • Key Topics

    • OS: processes, threads, scheduling, memory management.
    • Networking: TCP/UDP, HTTP, DNS, proxies, SSL/TLS.
    • DBMS: indexing, normalization, transactions, isolation.
    • CAP, ACID, BASE, consistency models.
    • AWS basics: EC2, S3, RDS, SQS, CloudWatch.
    • CI/CD & Observability: pipelines, monitors, alerts.

  • Final Week Activities

    • Mock interviews (see interview-prep-playbook.md).
    • Re-solve key machine coding and DSA problems.
    • Review system design notes and practice whiteboarding.

Cross-links

  • Day-wise plan: week-16.md.
  • Theory details: theory-round.md.
  • Schedules & metrics: schedules-and-metrics.md.