System Design Classroom

A Good System Design Tackles Down the Hot Path First

Before you add cache, replicas, queues, or microservices, understand where the system actually feels pressure.

Jun 13 • Raul Junco

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May 2026

Most System Design Mistakes Hide Between the Boxes

Five gaps your architecture diagrams don't show

May 30 • Raul Junco

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Bad Retries Can Break Good Systems

A practical guide to using backoff, jitter, retry budgets, idempotency, and circuit breakers in backend systems.

May 9 • Raul Junco

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April 2026

Event-Driven Systems Are Easy to Build but Hard to Keep Correct

4 ways event-driven systems fail without looking broken

Apr 25 • Raul Junco

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Consistency is negotiable. But the bill always lands somewhere.

Linearizable, causal, eventual, and quorum: how to pick the right consistency guarantee for each workflow in your system.

Apr 18 • Raul Junco

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Good System Design Starts With Constraints, Not Diagrams, Not Tools

Most Engineers Learn System Design Backwards

Apr 4 • Raul Junco

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5

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March 2026

Async systems scale your system… and your problems.

Many developers only realize it after consistency breaks.

Mar 28 • Raul Junco

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Refactoring Databases Is a Different Animal

A practical pattern for evolving database schemas without breaking production

Mar 14 • Raul Junco

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

They show up disguised as simple data questions.

Mar 7 • Raul Junco

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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

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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

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December 2025

Happy Teams Build Better Products

6 lessons every engineer eventually learns the hard way.

Dec 12, 2025 • Raul Junco

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