This about the desire to keep things consistent.

When a development team makes a change to a component that is part of a large system they can be proud of their implementation. It can becomes the “way things are done”. The rest of the code base is shunned because it doesn’t follow the new standard. Now there is a desire to go through the rest of the system the improve it in the same way.

Stop, wait!

  • How long is this going to take?
  • When we the team get back to delivering business features?
  • Are these changes really needed?

These are the questions hiding in the background. These are the questions some delivery team will brush under the carpet.

I can totally buy the argument that if you change the look and feel of your application in one place there are good reasons to ensure consistency across the whole application. Your users may become confused by inconsistent interface.s They may stop using your software as a result.

What I don’t buy is the assumption that  consistency should stop you releasing a new feature. Perhaps you are trying something out that looks brilliant to the delivery team but when rolled out might causes your users to run a mile. In these circumstances the impact of the new feature should be measured. Only then will you know the true impact.

So when inconsistencies can impact you value stream I can be to swayed. But when I here technical arguments that say that we have to stop delivering new features for a while because this code change that was made to component A now need to be implemented across components B, C, D and E.

Often A, B, C, D, E are independent logical services. So the argument is saying because we changed A, we also need to change B, C, D & E. This same to contradict the assertion that services should be independent. Are we really arguing that the cost of changing one service increases exponentially as we build new service?  That makes no sense. We have a service based architecture to decrease costs not increase them.

Services communicate through interfaces to reduce implementation coupling

Services communicate asynchronously to reduce temporal coupling

Enforcing consistency across a code base causes build time coupling

I total empathise with the delivery teams OCD when they open up the code and see that services A and B have a terrible implementation when compared to services C’s elegant version. But in constantly evolving code base, the code will never be perfect at any point to time. You can never stop the clock and make everything perfect and even if you could, the moment time started running again the code would diverge and perfection would dissolve. In this way a code base demonstrates entropy. Over time and without a positive influence a code base will tend to disorder.

Dealing with this as technical debt. When improvements are spotted log them and even spend an hour or so improving  them yourself. But be cautious. If you have improved some code in a service that is not part of the feature set your team is working on that code may not be released in the short term. It may never get released.  It has no value if it is not released, so it is important to ensure that you don’t get distracted from the work you “should” be doing.

But lets follow this dark path a little bit more. Lets say you have invested the time and you want to realise the value of the work. Now you have to release this service alongside the rest of the team’s work. Ideally this would have little impact but experience tells me

  1. The release process will be very so slightly more complex
  2. There are more things to go wrong
  3. You get more questions about why “Service B” needs to be released when this increment is about changes service A

More effort, more time and more cost. You have coupled your change to the bulk of the team work purely for consistencies sake. Expand this problem to many services and you’re back to your monolith and you no longer can deliver cheaply, frequently and reliably. All this for consistencies sake.

If your application is such that you should drive for consistency at all cost –  you need to accept that impact and deal with the consequences – namely changes are likely to be slow. This should be a very rare case. If your priority is getting new features to your customer then you may have to deal with the fact that you application’s code may not be consistency.


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