Why Most Digital Banks Get It Wrong Before They Write a Single Line of Code

The global neobank market is expanding at a pace that would have seemed implausible a decade ago. The race to launch digital banking products has never been more competitive. Or more consequential. Yet for every Monzo, Revolut, or Chime that made it to market cleanly and quickly, there are a dozen banking ventures that burned through the runway, missed regulatory windows, and watched their competitive advantage erode while still in pre-launch.

But, why? The business case can seem sound. The team is qualified. The funding was secured. So what can go that wrong?

More often than not, the answer lives somewhere in the earliest technical and architectural decisions.

Decisions that need to be made wisely before a single customer ever opens an account. There are many nuances to the decision, but it comes down to knowing which problems have been solved and what differentiates you.

The nuances of build vs buy

There’s a seductive logic to building everything in-house. It feels like ownership, like control, like differentiation. But in practice, teams that insist on building every component from scratch are making a strategic error they’ll spend years paying for.

A useful principle: if it doesn’t differentiate you in year three, don’t build it in year zero. Buy it.

Compliance infrastructure is the most common place teams fall into this trap. AML and KYC tooling, fraud detection, sanctions screening — these are solved problems. The vendor ecosystem is mature, well-regulated, and deeply integrated into how financial institutions operate globally. Global financial institutions spend billions on financial crime compliance and the cost only continues to rise with the advent of AI cybersecurity threats. 

Luckily, there is no shortage of proven solutions. Building a proprietary alternative from scratch isn’t innovation; it’s reinvention of the wheel, usually at the cost of your timeline. 

Regulatory reporting presents an even more dangerous blind spot. Many teams defer it, assuming they can just assemble the data and buy a vendor solution later. But reporting tooling can only be procured effectively if the underlying data architecture (which must be built) is designed with reporting in mind from day one.

Regulatory bodies don’t wait for data architectures to mature, and retrofitting reporting capabilities onto a live system is a brutal engineering challenge, especially if you are migration from legacy core banking safely. You can buy the reporting engine, but you have to build the foundation. Reserve your engineering talent for the problems only your team can solve.

What actually deserves to be built

So what should a digital bank own entirely? 

Two categories stand out.

The first is integration and orchestration logic. This is the connective tissue of a digital bank, how account opening flows end-to-end, how payment instructions are routed across rails and retried on failure, how limits are enforced across product types, how exceptions surface and resolve. These workflows sit at the intersection of your product logic, your third-party relationships, and your core banking system.

No vendor will build this for you in a way that reflects your specific proposition. You must maintain control and flexibility where it matters most. That means, build the orchestration layer internally for specific needs of the bank to maintain control and flexibility where it matters the most. The right core banking implementation partner can help you construct these custom workflows without sacrificing that critical ownership.

Data architecture falls into the same category. While it might not directly differentiate your product to a customer, data is the heart of every integration and enables you to build those differentiating features the right way. Because of that, you must maintain complete control internally. It is not glamorous, but it is foundational. Banks that underinvest here consistently find themselves optimising for the wrong things, building features in response to surface level signals because the underlying data fails to give them a clear picture of what is actually happening. In the 2024 Global Banking Annual Review, experts at McKinsey found that financial institutions with mature data capabilities outperformed peers on customer acquisition cost by up to 30%. That gap doesn’t emerge from better marketing. It emerges from better infrastructure.

The second category is customer experience. The mobile interface your customers will see as your first touchpoint and interact with daily. In a market where switching costs are low and alternatives are abundant, the app is often the first and most lasting impression a customer forms. Digital-native challengers have understood this from the beginning; many incumbent banks are still catching up. User experience is one of the few genuine differentiators visible at first contact, and it compounds: J.D. Power’s 2024 U.S. Banking Mobile App Satisfaction Study found that customers who rate their mobile banking experience highly are significantly more likely to expand their product relationship with that institution. The front end is not a polish exercise. It is a retention mechanism.

Rethinking where core banking falls in the decision

Core banking sits in a category of its own because it is simultaneously something you should buy and something you must configure deeply.

The mistake teams make is treating the core as a black box. Just selecting a platform and then working around its constraints rather than through its capabilities. Modern core banking platforms, from vendors like Thought Machine, Mambu, and 10x Banking, are built on the assumption that product teams will configure them extensively. For example, the best partner for Thought Machine implementation and others would know that: defining product parameters, composing propositions, and orchestrating workflows around the ledger logic the platform provides.  Because this configuration is a huge effort itself, banks should not save money on a proper implementation partner. A vendor with a track record will not only configure the products properly but will also advise on exactly which logic should go into the core and which should go into the orchestration layer.

What you should never be building is the ledger itself — the posting engine, the transaction processing layer, the financial audit trail. That infrastructure exists, it is robust, and rebuilding it serves no one. What you should be building is everything that sits above it: the logic that makes your current account different from a competitor’s, the rules that govern how your credit product behaves, the orchestration that ties your core to your payment rails to your third-party services.

The banks that launch cleanly tend to have internalized this distinction early. They treat the core as infrastructure and build their differentiation on top of it, rather than treating the entire stack as a construction project.

Launching fast, but without the added risk

There is a persistent assumption in the industry that launching fast requires compromising on product integrity or regulatory robustness. The evidence doesn’t support this. Fast launches and and well-built launches are not in opposition, they are the product of the same discipline: knowing which problems have already been solved and refusing to solve them again. However, going live quickly also requires ruthless prioritization. You have to look at your features through the lens of time. If an annual regulatory report is not due until six months after your launch, do not build it for day one. If customer offboarding can be handled manually by your back office initially, leave it out of your launch scope.

The digital banking sector added over 400 million users globally between 2021 and 2024. That growth reflects genuine consumer demand for better products. The opportunity is real. The question for any team preparing to enter the market is not whether to move quickly, but how to move quickly in a way that doesn’t require undoing half of what was built once the first customers arrive.

Build the things that make you different. Buy the things that don’t. And be honest, very early, about which is which. We have a banking team of experts and core banking migration consultants that have seen several fully digital banking projects launch in 18 months, not 36. Reach out to us and chat with them about all the nuances in build vs buy decisions.