Agile vs. Lean – Timeboxes vs. Flow

Agile uses the idea of fixed timeboxes where the scope of work completed for an iteration is estimated based on a duration such as 2 weeks. Importantly, even if all the planned work for an iteration isn’t complete, what has been developed is built and delivered anyway – the iteration is timeboxed and the schedule does NOT slip.  This ensures there will be some value delivered to the customer, even if it falls short of what was planned. But in lean thinking, the focus is on flow – the continuous flow of value rather than the incremental flow. In a discrete production context, this manifests as a striving to reach a batch size of 1 – rather than a ‘production run’ on a machine making 1000 widgets, it makes just 1 as it is pulled from the subsequent operation. This move to smaller batches and therefore towards continuous flow is possible because of new manufacturing technology – for example a machine that can be instantly reprogrammed can easily switch from making one type of widget to another. Similarly, in software development, we strive for ever smaller increments, ever shorter iterations.  And, like production, this is enabled through technology such as automated testing and continuous integration. These technologies reduce the cost of testing, building and deploying and allow us deliver value in a way approaching the ideal – continuous flow – advocated by lean philosophy.

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