Microservice summary

Data in Microservice

Each service gets its own database (if it needs one)

Services will never, ever reach into another services database

Ok, but why??

Why database-per-service

• We want each service to run independently of other serices
• Database schema / structure might change unexpectdely
• Some services might function more efficiently with different types of DB’s (SQL vs NoSQL)

Sync communication between services

Sync: Services communicate with each other using direct requests

Async: Services communicate with each other using events

Notes on Sync communication

Pros

• Conceptually easy to understand
• Service won’t need a database

Cons

• Introduces a dependency between services
• If any inter-service request fails, the overall request fails
• The entire request is only as fast as the slowest request
• Can easily introduce webs of requests

Pros and Cons with Asynchronous communication

Pros

• Service has zero dependencies on other services
• Service will be extremely fast

Cons

• Data duplication. Paying for extra storage + extra DB
• Harder to understand