System Design Classroom

Every repeated LLM call is money on fire

Redis 8 just changed the game with semantic caching that understands meaning, not just keys.

Aug 11 • 

Raul Junco

76

7

July 2025

Retries Have an Evil Twin: Duplicates

Every distributed system has a duplication bug; it just hasn’t been triggered yet.

Jul 28 • 

Raul Junco

39

7

Your Database Doesn't Trust the Server. That's Why It Writes Everything Twice.

What Every Backend Engineer Should Know About Write-Ahead Logs

Jul 9 • 

Raul Junco

84

8

June 2025

High Availability Isn't About Luck

It's About Patterns.

Jun 26 • 

Raul Junco

60

3

Distributed Transactions Are the Root of All Complexity

SAGAs provides a structured way to deal with them.

Jun 19 • 

Raul Junco

80

5

Dead Letter Queues Are Not Your Safety Net

They’re a visibility tool. Most teams misuse them, and lose data silently.

Jun 14 • 

Raul Junco

53

4

You can learn System Design while waiting for your coffee.

A coffee shop operates like a Distributed System; You will learn how below.

Jun 11 • 

Raul Junco

565

43

May 2025

Most Systems Get Consistency Wrong

DynamoDB Shows How to Do It at Scale

May 31 • 

Raul Junco

56

4

Everything Started with the Promise of Loosely Coupled Systems

Lessons from using Event-Driven Architecture

May 17 • 

Raul Junco

80

6

Every Outbox Needs an Inbox

At-Least-Once + Idempotency using Outbox and Inbox patterns.

May 3 • 

Raul Junco

67

6

April 2025

What if this happens twice?

The Painful Truth About Retries, Replays, And The Myth Of Perfect Delivery.

Apr 24 • 

Raul Junco

51

6

Why Just Publishing Events Isn’t Enough

Domain Events vs Change Data Capture: The Hard Truth About Using the Right Pattern for the Right Job

Apr 19 • 

Raul Junco

 and 

Marcos F. Lobo 🗻🧭

64

10