Michał Plechawski - CIO/CTO - mBank: Why "Big Bang" IT Migrations are a Terrible Idea (And What mBank Did Instead)

Why "Big Bang" IT Migrations are a Terrible Idea (And What mBank Did Instead) 🚀

Every technology leader knows the dread of a "Big Bang" migration. You hold your breath, flip the switch, and pray nothing breaks. But what if you could change the engine of a plane while it is still flying? ✈️

In our latest CIONET Podcast, Michał Plechowski, CIO & CTO at mBank in Poland, reveals how his team moved 12 million customers off a legacy mainframe without ever stopping day-to-day business operations.

Rather than gambling on a massive, high-risk cutover, Michał’s team built a clever "sharding" architecture that allowed the old mainframe and the new modern infrastructure to run in parallel. They migrated customers seamlessly in the background—starting with just 100 people (including Michał himself) and snowballing from there, complete with a full rollback safety net.

If you are tackling technical debt or planning a massive infrastructure overhaul, this interview is an absolute masterclass. Here is what you will discover:

  • How mBank dedicated just 10% of their IT capacity to the platform migration, leaving 90% of developers completely free to continue delivering new business features.
  • Why bowing to pressure and accepting a "Big Bang" release on a past project taught Michał a painful but invaluable lesson about risk.
  • A fascinating look at the psychology of change management, and how mBank successfully retained their veteran mainframe administrators by transitioning them to the new cloud age.
  • Why Michał believes the LLM and AI agent revolution completely rewrites the rules of enterprise software development.

Grab a coffee and learn how one of Poland's top digital banks successfully executed one of the most complex IT manoeuvres in the industry.

🔗 Register for the #CIONETAwards2027 to meet Michał! 

 


People also watch