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Mobile banking back ends

Mobile Banking App Development: The Back End Behind the App

We build the APIs, authentication, core-banking integration, notifications and caching behind a mobile banking app, in Java and Spring. Your team or a mobile partner builds the iOS and Android clients, and we design the API around their release cycle.

Book a scoping callBanking and fintech engineering

Back ends we built, measured in production

300,000,000
queries a day on a search back end we redesignedUK hotel metasearch engine
-60%
response time on the same system after the redesignUK hotel metasearch engine
1,000,000,000
financial transactions in under an hour on an in-memory ledgerFastPost, developed for Legerity from 2013
Who it is for
Banks and fintechs launching a mobile channel, and app teams that need a faster back end
What we build
APIs, strong authentication, core and card integration, notifications, caching and monitoring
What we do not build
The iOS and Android clients; we design the API for the team that builds them
How it is sold
A written ballpark, then modernization sprints or a time and materials build
Goals

What banks want from a mobile channel

Customers judge a bank by its app, and most of what they feel comes from the back end.

  • Screens that answer in under a second

    The platform caches and aggregates data, so screens stay fast even when the core behind them is slow.

  • Old app versions that keep working

    Versioned APIs, so customers who have not updated the app keep using it.

  • Strong authentication without friction

    Step-up only for the actions that need it, to the PSD2 rules and ready for PSD3.

  • An app team that ships every week

    API changes planned with the app team, so back-end work does not hold up a release.

What we build

What banking app development needs on the back end

  • API layer designed for a mobile client

    Screen-shaped endpoints, versioned so old app versions keep working, with the latency budget agreed up front and measured in production.

    Java development services

  • Authentication and session security

    Strong customer authentication, device binding, token lifecycles and step-up for sensitive actions, built to the PSD2 rules and ready for PSD3.

    Secure Java guide

  • Core and card integration

    Balances, transactions, payments and card controls read from and written to the core through an integration layer that survives the core's batch windows.

    Custom banking software

  • Caching for sub-second screens

    In-memory data grids where the core cannot answer in the time a screen has, with a clear staleness rule defined for each data type on the screen.

    Performance engineering

Case studies

Back ends that carry the load

All case studies

How we help

Services for mobile banking platforms

Where the delay comes from

Why banking apps are slow, and where the fix is

A mobile screen that waits on three synchronous calls to a core banking system will be slow however well the client is built. Caching, aggregation and asynchronous design behind the API make an app feel fast, and that is the Java engineering we did on a search engine answering 300 million queries a day.

We do not build the mobile client, and we do not subcontract it. On the scoping call we suggest how to split the work between your app team and ours.

Questions we get asked

Questions about mobile banking app development

Why not build the whole app?

Native mobile development is a separate discipline with its own release process, and taking it on would mean subcontracting it. We recommend a mobile team that owns the client and a back-end team that owns the platform, working in the same weekly rhythm.

Can you work with our existing core banking system?

Yes, and most of the work is there. The integration layer is designed around what the core can expose and how fast, including its batch windows, and caching fills the gap between that and what a screen needs.

How do you handle strong customer authentication?

To the PSD2 regulatory technical standards, with device binding, token lifecycles and step-up for sensitive actions, designed so the changes expected under PSD3 can be made through configuration.

Who owns the back end you build?

You do. It is built in repositories you control, ownership is assigned to you in the agreement, and handover is part of the scope if your own team takes it over.

Is your team big enough to work alongside ours?

A boutique team of senior engineers, all direct employees. That suits a back-end team working in the same weekly rhythm as your app team.

What technology runs behind the app?

Java and Spring for the API layer, an in-memory data grid for sub-second screens, Kafka for notifications and the activity feed, and the core's own interfaces behind an integration layer.

Go deeper

Mobile banking guides from our engineers

All articles

Written by , Co-founder and CEO, Stratoflow. Published . Updated .

Next step

Schedule a scoping call about your banking app

Thirty minutes with an engineer on your app, your core and what slows your screens, then a written view of scope.

Book a scoping callBanking and fintech engineering