Software Design & Architecture

OOP organizes large systems around objects and their responsibilities — the basis for most later patterns.

SOLID is five principles that make a design flexible, extensible, and easier to test and maintain.

Design patterns are proven solutions to recurring problems — a shared vocabulary and mature solutions instead of reinventing.

Architecture is the hard-to-change decisions — understanding it early prevents painful rewrites.

Separating business logic from details (DBs, frameworks) keeps a system testable and independent of tools.

DDD ties code to the real business language, so the code becomes a clear reflection of the problem domain.

Choosing the wrong style early is expensive — understand the trade-offs before splitting your system.

How services talk to each other determines a system's resilience, performance, and fault tolerance.

Data is the hardest part of distributed systems — storage and consistency choices shape the whole system.

Designing for millions of users requires understanding caching, load balancing, and horizontal scaling.

Pulling all principles together into a full system under real constraints is the true test of an architect.