How we're scaling up ING's mobile app to 6 countries:

insight into this ambitious and exciting tech project

'From 0 to 15 million users in 6 countries: a tech story on how to build a truly scalable app'. That's the title of the keynote Marcin Pakulnicki, IT Area Lead for ING's Mobile Banking APP, will be giving at DEV World 2024. The event takes place from 29 February to 1 March at RAI Amsterdam.

The app referred to in the presentation’s ambitious title is ING’s mobile banking app. It was initially developed for the Netherlands, but it is already forming the foundation for the Belgian app. And the Australian, German, Italian and Romanian apps will follow later this year, resulting in a user base of many millions of retail customers. That large scale presents an opportunity, but also the biggest challenge. Because how do you build a mobile app that is scalable and easy to expand to other countries, but that also meets the specific local wants and needs? Marcin will be sharing details of his own experiences during DEV World.

 Marcin: “A project like this includes multiple aspects. From software architecture and design, to a clear, complete product catalogue and setting up teams efficiently. It involves six different local markets, and ING has a different positioning and product offering in each one. For example, we don’t offer mortgages in all countries, and ‘payment request’ is a typical feature for the Netherlands. Therefore, we use different marketing methods for the app in each country and also have different release dates in the local app stores.”

Local developers contribute

The fact that the mobile banking app was not initially developed as a generic app (or ‘One App’ as it is called within ING) poses an additional challenge. “We’re building on top of the Dutch-Belgian app. The central development team always makes a country-specific copy of the basic app. In our model of working, the local developers actively contribute content and features for use in their own market, and these can sometimes be used in other countries too.”

“For example, contributions from local developers – in this case in Germany – have already resulted in Apple Pay being integrated into the app in all countries. Needless to say, the local teams have a lot of contact with each other; we’re constantly exchanging knowledge and ideas. We hold technical meet-ups and ‘mobile meets mobile’ conferences, which are very well attended by mobile developers from all countries.”

Huge number of customers

“It’s obvious that the developers really appreciate the way we work. It’s cool to work for such a huge number of clients, of course, but it can also be daunting. In the Netherlands alone, we have 7.5 million logins a day on the app. New features have to be perfect, down to the tiniest details; the large scale and high visibility mean you can’t afford to make any mistakes. The mobile app is one of ING’s most important assets. We want our customers to be able to take care of everything themselves using the app, so there’s quite a lot of pressure.”


“We also provide the backend systems, which are another big responsibility. The payment module in One App has to work for payment processes in all the countries that are connected to the app, so reliablilty and monitoring are crucial. That aspect of our work is mission-critical. If any part of it isn’t working properly, we really do have a serious problem.”

Beneath the bonnet

Marcin’s keynote will cover these challenges, opportunities, lessons learned and successes. He will also show how the common features work, and how they are presented differently in each country. “The audience will get a peek beneath the bonnet of a large-scale app. They will also see how ING tackles this huge task, plus – and I can’t stress this enough – what an attractive and interesting tech company we are.”

Interested to hear Marcin's keynote? Register at DEV World 2024.

Having previously held various other tech roles at ING, Marcin has been responsible for ING's mobile banking app as IT Area Lead since mid-2022. He taught himself computer coding and initially started out as a Flash developer. Marcin is a big fan of science fiction movies and Eastern European science fiction writers. Check Marcin's LinkedIn profile here.

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