System Design Classroom

Refactoring Databases Is a Different Animal

A practical pattern for evolving database schemas without breaking production

Mar 14 • Raul Junco

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5

CAP questions almost never appear labeled as “CAP theorem.”

They show up disguised as simple data questions.

Mar 7 • Raul Junco

92

6

12

February 2026

A Single Subscriber Doesn’t Turn Pub/Sub Into a Queue

Why execution semantics -not tooling- define async patterns.

Feb 28 • Raul Junco

47

2

1

January 2026

80% Of The Times, Scaling Is Not a Rewrite Problem

How a single interview question reveals who understands load, risk, and trade-offs

Jan 10 • Raul Junco

55

2

3

December 2025

Happy Teams Build Better Products

6 lessons every engineer eventually learns the hard way.

Dec 12, 2025 • Raul Junco

29

3

1

October 2025

Performance Doesn’t Start at SELECT; It Starts at CREATE.

Stop blaming your queries. Most database slowness comes from design mistakes made on day one.

Oct 28, 2025 • Raul Junco

121

13

8

CDC Isn’t the Shortcut You Think It Is

7 hidden costs of “free” event publishing

Oct 7, 2025 • Raul Junco

54

3

1

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, 2025

45

2

5

Most Engineers Want Both Consistency and Scalability.

Reality Doesn't Work That Way.

Sep 25, 2025

72

7

4

To Cache or Not to Cache

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

Sep 16, 2025 • Raul Junco

104

13

9

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, 2025 • Raul Junco

85

10

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, 2025 • Raul Junco

45

7

4