System Design Classroom

CDC Isn’t the Shortcut You Think It Is

7 hidden costs of “free” event publishing

Oct 7 • 

Raul Junco

41

3

September 2025

What Uber’s Slackbot Taught Me About Building Smart AI Assistants

Forget dashboards. The fastest path to insight is an agent that speaks your data’s language.

Sep 30

32

2

Most Engineers Want Both Consistency and Scalability.

Reality Doesn't Work That Way.

Sep 25

61

7

To Cache or Not to Cache

A 7-question framework for making caching a design decision, not a default.

Sep 16 • 

Raul Junco

93

13

August 2025

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

84

10

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

44

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

87

8

June 2025

High Availability Isn't About Luck

It's About Patterns.

Jun 26 • 

Raul Junco

62

3

Distributed Transactions Are the Root of All Complexity

SAGAs provides a structured way to deal with them.

Jun 19 • 

Raul Junco

83

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

55

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

569

43

May 2025

Most Systems Get Consistency Wrong

DynamoDB Shows How to Do It at Scale

May 31 • 

Raul Junco

56

4