Technique: Discover service boundaries (SOA)
February 4th, 2021
Search for 'natural folding lines' in the domain
Try to find the "natural folding lines" between areas in the domain.
how: ask domain experts:
"Can you imagine that changing data x ever impact data y"
eg. "[hospital] Would the patient changing family name impact which doctor they get treated by"
eg. "[webshop] Would changing the description of a product cause the price to change?"
When the domain expert looks at you like
- "You don't get it at all do you?"
Then you know you've got a 'natural folding line'
Technique: Discover service boundaries
Apply use cases one by one
Grow your data model + messages between
Limit the amount of data that needs to be exchanged between services
cluster data into services ('needs to be' together)
make a decision
most decisions will be wrong
every wrong decision will lead you astray
do it anyway
don't name the clusters!
only meaningless names allowed for conciseness
random colors: the green cluster, the purple cluster
random letters: cluster A, cluster B
meaningful names attract 'data related to the name'
even when it does not need to be together
once you get stuck with too much coupling, reset (or revisit a clustering decision)
You'll know when you have found the 'right' boundaries.
But you can't predict how many attempts it will take...
Pattern: Global ID
share the global ID between services