README.md

Tasks

• Analyze business requirements and technical details
• Clarify questions with the customer
• Create system design diagram
• Create entity relationship diagram
• Setup NestJS monorepo
• Create Prisma schema file based on ERD
• Create Dockerfile for service app and worker app
• Create docker-compose.yml file
• Connect to external BTC-to-UAH API
• Configure Prometheus and prom-client
• Create endpoints
  • GET /rate
  • POST /rate
  • GET /emails
  • POST /emails
  • DELETE /emails
  • GET /metrics
• Collect metrics
  • subscribe email count
  • unsubscribe email count
  • send email success count
  • send email error count
  • exchange rate gauge
• Get exchange rate every hour
• Get exchange rate at 9 AM Kyiv time
• Use CQRS pattern
• Use Nodemailer for mailing
• Use Bull for task queuing
• Use Cron/Interval for task scheduling
• Use Pino for logging
• Add unit tests

System Design Diagram

Entity Relationship Diagram

Services

• localhost:3001 -> Service App (/api -> Swagger Docs)
• localhost:3002 -> Worker App
• localhost:9090 -> Prometheus
• localhost:6379 -> Redis
• localhost:5432 -> PostgreSQL
• localhost:5555 -> Prisma Studio (npm run db:studio, only in local dev)

Links

• https://www.bemyaficionado.com/design-a-notification-system
• https://blog.risingstack.com/node-js-performance-monitoring-with-prometheus/
• https://mailtrap.io/ (email delivery testing)