Understand the concept
Start with the problem a component solves and where it fits in a real architecture.
Free Engineering Resources
Learn software engineering one concept at a time.
Explore practical, interview-focused engineering guides covering System Design, scalability, databases, distributed systems and backend architecture.
Free to readInterview focusedArchitecture diagramsMobile friendly
System Design Learning Path
Build your HLD foundation
01
Traffic
Load balancing & rate limiting
02
Data
Databases & caching
03
Communication
Queues & asynchronous systems
04
Entry Layer
API Gateway & service routing
6
HLD Topics
Free
Access
HLD
Focus
Concepts
Clear explanations
Architecture
Visual system flows
Trade-offs
Production thinking
Interviews
Focused revision
Now Available
Core engineering resources
Two complete resources are now live: SQL for database engineering and API Engineering for designing reliable production APIs.
2 complete guides
Database
SQL
Master SQL from fundamentals to advanced queries, joins, subqueries, CTEs, window functions, indexes, transactions, ACID, locking, optimization and interview problems.
Learn this topic
Backend
API Engineering
Learn REST, RESTful API design, HTTP, GraphQL, authentication, authorization, pagination, idempotency, caching, rate limiting, webhooks, OpenAPI and production API architecture.
Learn this topic
Recommended learning path
Start with SQL to understand how application data is stored, queried and optimized. Then move to API Engineering to learn how backend systems expose, secure and scale access to that data.
SQLAPI Engineering
System Design / HLD
High Level Design resources
Build your system design foundation through focused topics covering the components that appear repeatedly in backend and HLD interviews.
Performance
Caching
Learn cache-aside, write-through, write-back, TTL, eviction policies, Redis, distributed caching, consistency and cache invalidation.
Learn this topic
Scalability
Load Balancing
Understand load balancers, Layer 4 vs Layer 7, routing algorithms, health checks, sticky sessions and high availability.
Learn this topic
Data
Database Design
Learn SQL vs NoSQL decisions, indexing, replication, sharding, transactions, consistency and database scaling trade-offs.
Learn this topic
Async Systems
Message Queues
Understand asynchronous processing, producers, consumers, retries, dead-letter queues, ordering and event-driven systems.
Learn this topic
Reliability
Rate Limiting
Learn token bucket, leaky bucket, fixed window, sliding window and distributed rate limiting with Redis.
Learn this topic
Microservices
API Gateway
Learn routing, authentication, authorization, throttling, BFF, aggregation, retries, circuit breakers and gateway security.
Learn this topic
How to use these resources
Learn system design in a practical sequence
Each resource is designed to help you understand the component itself and how it participates in a larger distributed architecture.
See the architecture
Use diagrams and request flows to understand how clients, infrastructure and services connect.
Study trade-offs
Learn when a solution works well, when it fails and what alternatives an interviewer may expect.
Prepare for interviews
Revise common questions, failure cases, scaling decisions and production considerations.
Growing resource library
More engineering topics are coming
The free resource library is continuing to expand with backend, Java, Spring Boot and DevOps learning tracks.
Coming Soon
Backend Engineering
APIs, authentication, concurrency, distributed systems, queues, caching and production backend patterns.
Coming Soon
Java
Java fundamentals, OOP, collections, concurrency, JVM concepts and interview-focused engineering topics.
Coming Soon
Spring Boot
REST APIs, dependency injection, persistence, validation, security and production Spring Boot practices.
Coming Soon
DevOps
Docker, CI/CD, cloud deployment, monitoring, scaling and practical production operations.
Resources vs books
Use free resources for focused concepts. Use books for complete preparation.
The resource library helps you learn individual components. TargetTrek books connect those components into complete interview-ready systems and structured learning paths.
Free Resources
Best for learning a specific concept such as caching, rate limiting, databases or API gateways.
- Focused topics
- Quick revision
- Architecture basics
- Interview questions
Structured Books
Best when you want an end-to-end path covering multiple topics, design decisions and full interview systems.
- Complete learning path
- Detailed system designs
- Trade-offs & edge cases
- Interview preparation
Why TargetTrek resources
Built around engineering understanding, not memorization
The goal is to help you understand why a component exists, how it works and how to discuss its trade-offs.
Architecture first
See where each component sits in a complete system.
Developer focused
Explanations are written for software engineers and backend developers.
Trade-offs included
Understand failure cases, reliability and production concerns.
Interview ready
Connect concepts with the questions commonly discussed in system design interviews.
Keep learning
Build stronger system design fundamentals.
Start with free HLD resources, then move into complete system design preparation when you're ready.