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Practical notes on architecture, trade-offs, and code you can run in production.

ArchitectureJun 25, 20266 min read

Domain Events: The Contract That Decouples Without Breaking the Domain

Who else needs to know once the money has already moved? I asked myself that with the ledger freshly done and no topic running yet. That week I split what happened in the domain from the message Kafka will carry next.

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ArchitectureJun 24, 20265 min read

Internal Ledger: One Transfer, Two Entries, Zero Negative Balances

How do you prove the money moved if the client retries after a timeout? I asked myself that while picturing a balance column and an UPDATE again. That week I wrote movements you never delete

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ArchitectureJun 23, 20264 min read

Modeling Money in Code: Cents, bigint, and Why float Doesn't Belong in a Banking Core

What happens when money stops being a number and becomes a responsibility? I asked myself that looking at amountCents in my POST /transfer draft. That day I wrote Money.

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ArchitectureJun 19, 20265 min read

Why I Start With a Modular Monolith (Not Six Microservices)

Six boxes on the diagram. Six microservice temptations. I almost fell for it again — until I got that the full map doesn't mean shipping it all in week one, and splitting repos doesn't split the domain

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ArchitectureJun 17, 20269 min read

There Is More Behind POST /transfer Than an Endpoint

Three seconds on the spinner. Timeout on screen. Did the money move? I reopened my Arkano challenge next to a fintech architecture map — and understood why POST /transfer was never just an endpoint.

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ArchitectureJun 15, 20265 min read

Why I'm Rebuilding a Fintech Core — From Zero, Slowly

A LinkedIn post on fintech architecture, a recent technical challenge, and a decision to rebuild a banking core from scratch — slower this time, to actually learn.

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ArchitectureApr 21, 20265 min read

How to Build a Multi-Tenant SaaS Application in NestJS Without Duplicating Your Code

If onboarding a new customer requires deploying a new application or duplicating an entire database, your SaaS architecture probably isn't ready to scale. Learn how to implement multi-tenancy in NestJS in a clean and maintainable way.

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ArchitectureApr 7, 20264 min read

Your API Doesn't Need More Services, It Needs Events

If every new feature forces you to modify five different services, you probably have a coupling problem. Learn how Event-Driven Architecture helps decouple modules and scale NestJS applications.

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ArchitectureMar 24, 20263 min read

CQRS in NestJS: Stop Mixing Reads and Writes in the Same Service

When your UserService handles POST and GET, optimizations on one side break the other. Learn commands, queries, and handlers with @nestjs/cqrs.

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ArchitectureMar 10, 20264 min read

Why Your NestJS Service Becomes a Mess (and How Hexagonal Architecture Fixes It)

Controllers that know too much, entities full of ORM decorators, and tests that need a database. A practical guide to ports and adapters in NestJS.

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