Iterate in Thens

You should iterate sequentially on a focused chunk of work at a time. Once that chunk has been completed THEN start on the next chunk of work. This is opposed to doing multiple chunks of different of work in parallel.


  • No context switching. Sequential working increases the chance that all relevant context associated with a chunk of work be kept in mind.
  • Reduced possible errors. Focusing on one change at a time, means the possible outcomes (e.g. bugs, regressions) from that change are much smaller than if many changes are made at the same time.


  • Define tasks in a sequential way.
  • When working, focus on a single task and capture additional tasks as a separate items.


Iterating on tasks by focusing on one chunk of work is better than trying to do too many things at once.

A example task is to upgrade 3 cores libraries that 10 applications use. Here are 3 approaches below:

  1. Go to the first application
  2. update library 1 AND 2 AND 3 at the same time
  3. THEN move on to the next application

The complexity arises through having to work with lots of different changes which can look like as follows:

  • Steps required to update 3 libraries.
  • Bugs arising from changing 3 libraries.
  • The complex interactions that may arise from changing 3 libraries at the same time.
  • Identifying which library a bug came from.

There is much to keep in mind with this approach.

Iterating in "THENs" approach:

  1. Go to the first application
  2. update library 1
  3. THEN move onto to the next application

This approach greatly focuses the context on an individual library and all the associated bugs or changes required.

The complexity is reduced to:

  • steps required to update a single library.
  • bugs arising from changing a library.

Iterating in "THENs" in parallel:

Iterating in thens also allows working in parallel. The parallel task should done sequentially with the task being mostly the same for each.

  1. With all the 10 applications search for the old library version
  2. THEN replace with the new version
  3. search for the old library method that is deprecated
  4. THEN replace with the new supported method.
  5. etc..


  • Chunk of work - Work that is divided up into related sections.