Priority Ranking (Master These in Order)

Priority	Topic	Why It Matters
1	Authentication , Authorization and basic System Design	Security is step 0. Fail here, and you lose everything.
2	Caching	Optimize reads, reduce DB load, scale apps smartly.
3	Queues & Workers	Async systems = resilient, scalable architectures.
4	Rate Limiting	Protect APIs from abuse, DDoS, and spam.
5	Observability	If you can't see issues in prod, you're flying blind.
6	Scaling	Survive success. Scale apps horizontally, not just vertically.
7	Security	Prevent exploits, breaches, and PR disasters.
8	Database Design & Optimization	Strong schemas = healthy apps. Weak schemas = silent killers.
9	API Design Best Practices	Clean APIs = faster dev, fewer bugs, happier users.
10	Concurrency & Parallelism	Speed + efficiency = critical at scale.
11	File Storage & Management	Handle file uploads, backups, and delivery like a pro.
12	Deployment & CI/CD	Real devs ship often, reliably, automatically.

Study Phases

Authentication & Authorization
- Learn Sessions, JWTs, OAuth2.
- Build RBAC into a simple blog app.
Caching Basics
- Redis cache-aside pattern.
Rate Limiting
- Protect APIs with Redis counters.
Database Fundamentals
- Master indexing, constraints, normalization.

Mini Project:

Queues & Workers
- RabbitMQ or Kafka basics.
- Retry strategies, dead-letter queues.
Load Balancing etc.
- Load balancing algorithms (e.g., round robin, least connections), proxy, reverse proxy and how to configure a load balancer (e.g., NGINX, Traefik) with health checks, SSL termination, and scaling strategies.
Observability Stack
- JSON logs, Prometheus metrics, Grafana dashboards.
API Design
- RESTful principles, versioning, pagination.
File Storage
- S3 (or local storage abstraction).