Change wings on the fly: how we replaced a system that handles several million euro turnover with zero downtime.

In October 2019 Diggecard, a Norwegian fintech startup, acquired a UK gift card company. One of the conditions of the deal was to move more than a hundred of their business customers off the systems they were using in less than a year without interrupting the service even for a day. This meant designing and developing the replacement software and of course, not just copying the existing one, but optimising it too. My role as Head of Design was to help development team make it happen. We did make it happen:

• planed the new system so that it fully replaced all old ones, leaving no holes;
• were at any time sure what would be the next piece of software that we need to develop;
• released new functionality in small portions that was immediately taken in use without necessity to wait for some other piece to be ready;
• met the deadlines in spite of additional complications caused by the pandemics. This was not just luck. It was the result of application of a methodology that ensures this very result: product that covers end-to end flow, minimal releases and clear priorities. In this case study I will show how this methodology works.