Many people don’t realize that Lean Software Development is based on the Toyota Production System (TPS). Toyota’s way of engineering cars is radically different than how most companies build cars. Instead of batch and queue (i.e. mass-production assembly-line), their manufacturing process is optimized for one-piece flow and pull-processes. Toyota’s way of building cars has demonstrated to produce higher quality products, increased productivity, faster time to market, and happier more accountable employees. Whereas assembly-line mass-production often results in over-production, lots of waste, and demoralized employees.
Achieving one-piece flow is about figuring out how to create a single quality unit as fast as possible while minimizing inventory, wait-time, transportation, hand-offs, etc. Through this process, the overall time from beginning to end is minimized to contain only all value-add steps. When there are defects in the manufacturing, the entire process must halt and the problem immediately fixed to ensure quality is built-in and there are no defects in the end product. Many organizations have problems implementing a true one-piece flow, it requires constant improvement, or kaizen.
Continuous Integration & Continuous Delivery (CI/CD) is the Toyota Production System’s concept of Flow applied to software development. At Toyota, the one-piece they’re making is a single car. In software, the analogous one-piece is a deployable software feature/task. Assuming trunk-based development and a modern containerized CI/CD setup, a developer typically writes code, runs unit tests locally and then commits it to a pull-request. As the pull-request is committed against, the new code is
There are pitfalls that people sometimes fall into while developing software. Sometimes people bundle multiple features into that deployable one-piece. Batching actually increases risk, when there’s more new code it increases the chance that something is defective. When something is defective, it now requires rolling back the batch of features instead of the single feature.
Sometimes people cut corners, they don’t write unit tests, integration tests or service tests. This is a false economy, you can’t have built-in quality if you don’t employ the right processes and safety nets. The engineers at Toyota say, “the right process will create the right results”. At Amazon.jp warehouses, they have a saying plastered everywhere, “safety is #1”. The same concepts apply to software development. The tests are the safeties.
There’s a lot of tooling that needs to be invested in to make one-piece flow work, sometimes people don’t spend the time investment to put the right machinery in place or continue to improve to make the processes more efficient (reducing waste). Good hygiene and exercise is necessary if you don’t want to get slow and fat.
Software can be complicated, the process of developing software doesn’t need to be.