EXCLUSIVE: “Blooming Good Returns” – Karishma Jaycee, Mambu in ‘The Fintech Magazine’

Paragon Banking Group leveraged Mambu’s composable core banking architecture to launch its successful savings app Spring, using open banking to effortlessly grow deposits.

Savers have been letting hundreds of billions of pounds sit in UK high street current accounts and easy-access savings accounts, where they earn little or no interest, for years. Recent analysis by the Spring savings app from Paragon Bank showed that of the 86.3 million UK current accounts in credit in November 2025, 87 per cent of them did not pay a single penny in interest – and the
average deposit was reported to be £4,300.

Customers have – until now, perhaps – been too lazy or too scared to move their cash to somewhere that gives them a better return. But the UK’s cost-of-living crisis and the trend for consumers to embrace digital banking (a 2025 YouGov poll showing that 73 per cent of British adults used a bank’s digital app over the past year) has created both risk and opportunity around savings accounts for high street and challenger banks alike. If they can successfully combine inflation-beating rates with an enticing digital experience, legacy banks can lock in customers to prevent liquidity drift.

Fully regulated challengers like Spring, meanwhile, will find it easier to entice customers away from those that don’t. So believes Karishma Jaycee, Customer Success Manager at the software-as-a-service (SaaS) core banking platform Mambu.

“It’s for [the banks] to bring these two things together and create a compelling savings proposition with the right user interface and digital experience that makes the customer feel that they’re in safe hands and that their money is growing – and that they also have visibility of it,” says Jaycee.

Paragon Banking Group has proved it. The West Midlands-based lender and savings bank has been supporting individuals and small businesses, who are traditionally underserved by large high street banks, since 1985. Starting life as a specialist residential mortgage lender that helped pioneer buy-to-let lending, Paragon went on to launch its first mortgage products for private landlords in 1995, achieving a 10 per cent share in the buy-to-let market by 2006. In 2020, it partnered with Mambu over its development finance and savings proposition.

“That’s where the trust and capability were really established, because, over time, Paragon has grown significantly,” says Jaycee. “You can see that by their savings portfolio, how strong their proposition is right now. All of that was made possible with a reliable, robust core banking engine, which is Mambu.”

It points to the fact that banks need to get the proposition right from the outset to lure savers, with a technology foundation that is both flexible and resilient, she says.

Mambu offers a fully Cloud-hosted SaaS composable banking solution, optimised for APIs. Its modular and future-ready model enables banks like Paragon to easily ‘plug in’ other services and third-party solutions, as and when required, and scale services quickly. Institutions in more than 65 countries rely on Mambu, including Western Union, Commonwealth Bank of Australia and Raiffeisen Bank, alongside fintechs, retailers, credit unions and other organisations, collectively serving more than 230 million end users worldwide.

Last year, Paragon used Mambu’s core banking platform to power its new savings app Spring, launched in partnership with open banking platform Moneyhub. The app enables a user to seamlessly connect their current account, no matter which bank it’s held at, and effortlessly automate regular and one-off deposits to grow their savings using open banking rails.

Allowing customers to make automatic savings through a simple sign-up removes any friction for the user, who may not feel confident enough or have the time to make decisions on how to make their money go further. The app also enables them to arrange their money into individual savings pots, while allowing the user to withdraw money at any time, with no fees, no fuss.

Jaycee signed up to Spring herself.

“I’ve been able to maintain my relationship with an existing bank, but also to make the most out of my money,” she says. Mambu was the foundation for Paragon’s wider greenfield transformation, says Jaycee. “And now they are really paving the way with their traditional savings and lending proposition, by adapting and evolving to market needs.

“To launch something like Spring, requires being able to connect to multiple providers and suppliers… And as Mambu is API-first, Paragon could rely on it to seamlessly connect all these”

Karishma Jaycee

“Customer demands are changing v ery rapidly now, so banks need to be able to turn these ideas into a market offering quickly. That was made possible at Paragon by using a reliable core banking engine that’s composable, API-first and allows a bank to easily and quickly launch new products to market.

“Something like Spring relies on being able to connect to multiple providers and suppliers, so they have a full market offering,” Jaycee continues. “And as Mambu is API-first, [Paragon] had full confidence it could rely on Mambu to enable it to seamlessly connect all these components.”

Results-driven transformation Spring is part of a wider digital strategy at Paragon, which is delivering results. In December, the London-listed company generated pre-tax profits of £256.5million in the year to 30 September 2025, up by 1.1 per cent from £253.8 million in 2024. Its net loan book grew by four per cent from £15.7billion to £16.3billion.

Speaking when the results were announced, CEO Nigel Terrington said: “Operationally, we’ve made significant strides in digitalisation this year. The successful launch of Spring, our new app based savings brand, and the rollout of our digital buy-to-let origination platform represent major milestones in our technology transformation.

“These developments are delivering tangible benefits for customers and driving efficiency across the group.”

According to Jaycee, it’s all about getting the foundation right; using enterprise composable architecture will allow Spring to scale thoughtfully, because, in her view ‘real success isn’t necessarily a huge spike in deposits, it’s about sustainable growth’.

Paragon tested its new app first with staff, family and friends to ensure that what it was launching was reliable, scalable and ready to be delivered to the end customer. And allthat diligent research appears to have paid off, judging by Spring’s Trustpilot scores. Its ‘excellent’ reputation is based on customer praise for the app’s user-friendliness, fast account setup, and competitive interest rates. Its easy integration with current accounts for fund transfers is often highlighted.

So, the differentiator is clearly not just competitive interest – several providers offer similar returns, after all. Rather, it’s favourable rates combined with the digital experience and ease of use being offered by a trusted, FCA-registered bank, says Jaycee.

Paragon serves as a prime example of how a bank can build a new digital product for customers, differentiating its offering enough to lead in the market. User experience is everything, Jaycee stresses.

“The banks that are winning, or going to win, aren’t the ones just with the best rates. It’s the ones that make you feel like doing the right thing with your money is effortless.”

While Paragon’s digitalisation journey is impressive, it’s success story is not unique among Mambu’s client portfolio.

“We have a lot of Mambu customers who are using us for their savings and lending proposition to keep up with the market and changing customer expectations,” observes Jaycee.

“It’s no longer just about bringing a new savings product to market. It’s also about making the product that you’re offering accessible to the end customer.”

This article was published in The Fintech Magazine Issue #38, Page 06-07