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Overview

HLD Roadmap

January 21, 2026
2 min read

PHASE 1 – Foundations

Goals

  • Understand scalability basics
  • Learn distributed system fundamentals
  • Understand trade-offs

Concepts to Master

  • What is High-Level Design?
  • Latency vs Throughput
  • Horizontal vs Vertical Scaling
  • CAP Theorem
  • ACID vs BASE
  • Consistency Models
  • Availability & Fault Tolerance
  • Load vs Stress vs Spike testing

YouTube


Reading

  • System Design Interview – Alex Xu

    → Chapter 1 (Scaling from 0 to 1M users)

PHASE 2 – Core Components

Goal

Understand all building blocks deeply.


Load Balancers

  • What is Load Balancing?
  • Round Robin
  • Least Connections
  • Sticky Sessions
  • L4 vs L7

Databases

SQL

  • Indexing
  • Normalization
  • Transactions
  • Replication

NoSQL

  • Document DB
  • Key-Value Store
  • Wide Column
  • When to use NoSQL

Caching (Redis)

  • Cache Aside
  • Write Through
  • Write Back
  • TTL
  • Cache Invalidation

Message Queues (Kafka)

  • What is Pub/Sub?
  • Kafka Architecture
  • Partitions
  • Consumer Groups
  • Exactly Once Semantics

CDN

  • What is CDN?
  • Edge locations
  • Caching static content

Monitoring & Observability

  • Logging
  • Metrics
  • Alerting
  • Distributed tracing

Finish System Design Interview – Alex Xu Volume 1

PHASE 3 – Practice Real Systems

Goal

Start designing real systems.

For each system:

  • Clarify requirements
  • Estimate scale
  • Draw architecture
  • Define APIs
  • Design DB schema
  • Identify bottlenecks
  • Scaling strategy

Practice Systems

  • URL Shortener
  • Twitter News Feed
  • Instagram
  • WhatsApp / Chat App
  • Rate Limiter
  • Distributed Cache
  • Notification System
  • E-Commerce Checkout

PHASE 4 – Deep Knowledge

Books

  • Start Volume 2 of Alex xu book

  • Designing Data-Intensive Applications

    Focus on:

    • Replication
    • Partitioning
    • Transactions
    • Consensus
    • Stream Processing

Read Blogs and videos for advanced designs