Feature: Add Note to Budget Command

[TMUCHIRI]

Backend development process
Implemented the write-side of a new feature using the existing CQRS pattern with @iote/cqrs. Commands are immutable payloads, handlers contain business logic and have access to repositories via the injected toolkit.

Design choices

• AddNoteToBudgetCommand includes validation and all required fields (budgetId, content, author)
• Handler extends FunctionHandler<Command, Result> – exact pattern used across the codebase
• Uses getRepository() from the CQRS toolkit (standard in all existing handlers)
• Simple demo ID generation (real Firestore would auto-generate)

Deployment
This handler will be automatically discovered and deployed as a Firebase Cloud Function (serverless) when the functions project is built and deployed – no extra configuration needed.

Serverless deployment & scaling

• Zero server management
• Automatic horizontal scaling to thousands of concurrent executions
• Pay-per-use pricing → extremely cost-effective for write-heavy or bursty workloads
• Cold starts are negligible for this size of function
• Stateless design fits perfectly with Cloud Functions / Cloud Run

Library created at: libs/features/budgetting/budget-notes