Stack chosen:

• Runtime system: Cats-Effect 3
• Persistence storage: postgresql(for simplicity)
• DB access: Doobie
• Http-server: Http4s
• Http-client for simulation: Sttp
• Db migrations: flyway
• Docs generation: Tapir

swagger docs: http://localhost:8080/docs/

DB Schema

  users
    id 
    username

  ads
    id 
    body
  
  impression
    id 
    user_id 
    ad_id 
    show_time 

  click 
    id 
    user_id 
    ad_id 
    action_time