System Design Classroom

Safe Database Rollback Starts Before Deployment

Learn why safe database rollback starts before deployment, and how backward-compatible schema changes, staged migrations, feature flags, and targeted…

24 hrs ago • Raul Junco

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How to Survive the Recommendation Engine Question

Most engineers focus on the matching algorithm. The real test is separating generation from serving.

Jul 11 • Raul Junco

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June 2026

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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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

54

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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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