System Design — Quick Reference Cheatsheet
Essential Formulas & Rules
Core Topics
Scalability (Horizontal vs Vertical):
Key formula/rule: See fundamentals section for complete derivation
When to apply: When the problem mentions keywords related to scalability (horizontal vs vertical)
Load Balancing:
Key formula/rule: See fundamentals section for complete derivation
When to apply: When the problem mentions keywords related to load balancing
Databases (SQL vs NoSQL, Sharding):
Key formula/rule: See fundamentals section for complete derivation
When to apply: When the problem mentions keywords related to databases (sql vs nosql, sharding)
Caching (Redis, CDN):
Key formula/rule: See fundamentals section for complete derivation
When to apply: When the problem mentions keywords related to caching (redis, cdn)
Message Queues:
Key formula/rule: See fundamentals section for complete derivation
When to apply: When the problem mentions keywords related to message queues
Microservices vs Monolith:
Key formula/rule: See fundamentals section for complete derivation
When to apply: When the problem mentions keywords related to microservices vs monolith
Problem-Solving Templates
Template 1: Identify → Apply → Verify
Template 2: For MCQs
Most Common Question Types
| Type | What to Do | Time Budget |
|---|
|---|---|---|
| Direct formula | Apply formula directly | 30-60 sec |
|---|---|---|
| Multi-step | Break into steps, apply each | 1-2 min |
| Concept-based | Recall definition + example | 45 sec |
| Data interpretation | Extract data, compute | 2-3 min |
Revision Strategy
1 month before exam:
1 week before:
1 day before:
Labs Section
The Labs section for System Design has: