🔹 SQL Example
BEGIN;
UPDATE accounts
SET balance = balance - 100
WHERE id = 1;
ROLLBACK;

🔹 Interview Tip
Transactions protect data integrity.

🚀 78. What is connection pooling?
Opening DB connections repeatedly is expensive.
Connection pooling: Reuses existing connections

🔹 Flow
App → Connection Pool → Database

🔹 Benefits
✅ Faster performance
✅ Reduced overhead
✅ Better scalability

🔹 Popular Tools
• HikariCP
• PgBouncer

🔹 Interview Tip
Connection pools are critical in high-traffic backend systems.

🚀 79. What is the CAP theorem?
CAP theorem states distributed systems can only guarantee TWO of:

🔹 CAP

C
• Meaning: Consistency

A
• Meaning: Availability

P
• Meaning: Partition Tolerance

🔹 Explanation

🔹 Consistency
All nodes return same data.

🔹 Availability
System always responds.

🔹 Partition Tolerance
System survives network failures.

🔹 Reality
In distributed systems: Partition tolerance is mandatory
So trade-off becomes: Consistency vs Availability

🔹 Interview Tip
CAP theorem is fundamental for distributed systems interviews.

🚀 80. How do you design a scalable schema for user-generated content?
Examples:
• Social media posts
• Comments
• Reviews
• Videos

🔹 Core Tables

🔹 Users
• user_id
• name

🔹 Posts
• post_id
• user_id
• content

🔹 Comments
• comment_id
• post_id
• user_id

🔹 Scalability Techniques
✅ Indexes
✅ Caching
✅ CDN for media
✅ Database sharding
✅ Async processing

🔹 Media Storage
Store images/videos in:
• Amazon Web Services S3
• Object storage systems

🔹 Feed Optimization
Use: Precomputed feeds for faster timeline generation.

🔹 Interview Tip
Scalable schema design focuses on:
• Read efficiency
• Write scalability
• High traffic handling

🔥 Double Tap ❤️ For Part-9