Work in small batches

Batch size decides how long you wait to find out whether you were right. Everything else about small batches follows from that.

The long way round

Phased delivery moves work in large lumps: developers hand a body of code to testers, testers hand it to a release manager, and each handoff waits for the previous stage to finish. Feedback on a decision made in week one arrives in week nine, by which time four other decisions have been built on top of it.

That model was expensive when the alternative was nothing. It is indefensible now that build, test and deploy can run unattended on every commit.

What small batches change

• Feedback arrives while you still remember the decision, and while it is still cheap to reverse.
• A small change is a small rollout. Less to review, less to verify, and one obvious suspect when something breaks.
• You can test a hypothesis, watch what happens, and course-correct instead of arguing about it.
• Finished work is visible weekly rather than quarterly, which is most of what keeps a team engaged.
• Problems surface individually instead of arriving as a pile at the end.
• You stop throwing good money after a bad assumption, because the assumption gets tested before there is much money in it.

Small batches also make decoupling deployment from release practical. Two hundred changes behind a flag is a release you are afraid of. Three is a switch you flip.

How to actually do it

• Break features into pieces that can be finished in days, not weeks.
• Make the pieces independent, so they can be built, deployed and tested in any order. This is the hard part and it is where the design work is.
• Sequence by importance. The first batch should be the one that teaches you the most.
• Ship each batch as something that works on its own and meets its own acceptance criteria. A batch that only makes sense alongside the next three is not a batch.
• Agree upfront that a batch can be revised once you have seen it running. Otherwise nobody uses the feedback the batches bought you.