From CRUD to Event Sourcing

Why CRUD is the wrong approach for microservices

James Roper



  • Failure test CRUD solutions
  • Learn about Event Sourcing
  • See why Event Sourcing is resilient
  • Live coding!

Holiday Rentals

  • Airbnb like application
  • Asynchronous microservice architecture
  • Kafka for messaging
  • Reservation service uses CRUD persistence


Service implementation

  • Basic approach:
    • Update database
    • Publish to Kafka

Naive approach

What if something goes wrong?

  • Is this approach resilent?
  • What if:
    • The service goes down?
    • The database goes down?
    • Kafka goes down?
    • The network goes down?

Naive approach

Another solution?

Two generals problem

Two generals problem

  • It is proven to be unsolveable

Two-phase commit

  • Can't we just use two-phase commit?
    • No.
    • Only reduces the window for failure to cause a problem
    • The window is largest when failure is most likely
    • Coordination comes at high cost

Too hard?

  • Maybe it's all too hard
  • Is inconsistency really that bad?

An easier way?

  • We can't solve the 2 generals problem
  • What if come up with a different plan of attack?

Event sourcing

  • Don't store the current state
  • Store the events that occurred
  • Compute the state from the events

Event sourcing

Event sourcing

Event sourcing

  • Advantages:
    • Fact centric approach
    • Self healing when problems occur
    • Built in audit log
    • Compute the state of the system at any time

Event sourcing

  • Details:
    • How is consistency addressed?
    • Is replaying events expensive?
    • How to query data?


  • CRUD is not an ideal fit for distributed systems
  • Event sourcing is an ideal fit for distributed systems
  • Event sourcing brings a host of other advantages

Next steps