Low-Level Design for MAANG Interviews

A book-shaped table of contents for LLD interview prep: OOP fundamentals through SOLID, design principles, UML, design patterns, dependency management, reliability, concurrency, domain modeling, API design, testing, refactoring, classic interview problems, advanced architecture, and performance — cross-linking Object-Oriented Programming and Patterns instead of duplicating them.

1 — Memory Optimization

Examines how object layout, field ordering, and reference graphs drive per-instance memory footprint and garbage collector pressure.

2 — Object Pooling

Reuses a fixed set of expensive-to-construct objects instead of allocating and discarding them, trading extra bookkeeping for reduced allocation churn.

3 — Lazy Initialization

Defers construction of a costly resource until its first actual use, at the cost of added complexity around thread safety and null checks.

4 — Caching Strategies

Compares eviction policies, invalidation triggers, and cache placement so repeated lookups can be served without recomputation or a round trip.