This usually starts the same way, a team comes with a clear idea. The flow makes sense. The user journey is clean. Everyone agrees it is straightforward.
Then it gets built.
And suddenly:
- one service times out
- another returns partial data
- retries create duplicates
- different teams implement the same thing differently
Nothing is “wrong” individually. But the system as a whole behaves inconsistently.
I have seen this enough times to know it is not a one-off.
The idea was clear. The behavior was not.
The Part Most Teams Skip
Most discussions stop at “what should happen”. Very few go deep into:
- what happens when things fail
- what is retried and what is not
- what happens if the same request comes twice
- which system is actually the source of truth
These are not edge cases. This is the system.
If this is not defined, every team fills the gap in their own way.
Where Things Actually Break
It is rarely one big mistake. It is a series of small, reasonable decisions.
Ambiguity Gets Pushed to Engineering
Specs are often high level. That sounds fine until engineers have to implement them. Then decisions show up like:
- do we retry this or fail fast
- do we block the user or continue
- do we accept inconsistent data or reject it
Different engineers make different calls. Now the same feature behaves differently depending on where you hit it.
“Let’s Keep It Flexible” Becomes a Problem Later
Flexible APIs and loose contracts feel fast at the start.
Later:
- no one knows what is guaranteed
- edge cases pile up
- small changes have unexpected impact
Every undefined behavior shows up in production eventually.
Local Decisions Add Up
One team adds a retry. Another adds caching. Another changes ordering. Each change is reasonable on its own.
Together, they create something no one fully understands. This is usually where platforms get pulled in to “fix” things.
What Changes When You Run the System
When you own systems that other teams depend on, your thinking changes. You stop focusing on happy paths.
You start asking:
- what breaks first
- how does this fail
- can we reason about this under load
You also start noticing a pattern:
Most issues are not caused by bad code. They come from unclear decisions.
What I Expect from Teams
This is not about more process. It is about being precise.
Be Clear About Behavior
If you are building a flow, you should be able to answer:
- what happens on failure
- what is retried
- what the user sees when things go wrong
If you cannot answer that, the system will behave differently than you expect.
Make Decisions Visible in the System
If something matters, it should not live in a doc. It should be visible in:
- the API
- the contract
- the validation
- the constraints
Otherwise it will be reinterpreted.
Understand the Impact of Your Decisions
Every shortcut has a cost. It does not disappear. It shows up later as:
- incidents
- inconsistent behavior
- extra complexity in shared systems
Most of the time, platforms end up carrying that cost.
A Simple Way to Think About It
A product describes what should happen. A system defines what actually happens.
Those two only match if someone takes responsibility for the details. If not, the gaps get filled in production.
Closing
This is the part that is easy to miss.
You are not just shipping features. You are defining system behavior.
If that behavior is unclear, the system will drift. And fixing that later is always more expensive.
If you do not define the behavior, production will.