Regions Bank chose a modern core. Here’s what that journey looks like.

Paul Weiss has spent decades running large-scale technology transformations. He knows what the complexity curve looks like, how it stops growing arithmetically at a certain scale and starts growing geometrically. When he joined Regions Bank as Chief Transformation Officer and inherited a core modernization already underway with Temenos, he knew what he was walking into.

What surprised him was the partnership.

“Very rarely have I had a partner that was as transparent and willing to collaborate as Temenos has been,” Weiss said. “Everything they’ve committed to, they’ve delivered. They’ve delivered on time.”

That kind of endorsement carries weight at this particular moment. Regions, with assets north of $155 billion, selected Temenos SaaS in 2023 to modernize its legacy systems for customer records and deposits, and is now roughly two years into an implementation that positions it to be one of the first large US banks to complete a move to a modern core.

The decision to go SaaS was deliberate. “We want to be able to focus on our customers and apply the functionality of the platform, rather than spending our focus on operating the platform,” Weiss said. Continuous upgrades, outsourced resilience, and the ability to redirect engineering attention toward customer outcomes rather than infrastructure maintenance drove the choice.

The goals were set before Weiss arrived. Regions is a customer-driven bank, and the legacy environment was working against that identity. Months-long product development cycles, extensive custom coding, friction at every point of the delivery chain. “The biggest thing we were looking for is end-to-end client responsiveness,” Weiss said, “with the flexibility that we can have with a new modern core.”

What Weiss brought to an already strong team was an engineering background and a specific discipline around managing complexity at scale. A core replacement at a bank like Regions means hundreds of integration points, each carrying its own data, compliance, and risk considerations, all of which have to move in concert. “Once you reach a certain scale, the complexity starts to increase geometrically, not arithmetically,” he said. “Thinking very carefully about how to manage complexity within the cost and timeframe that you have is a learned skill over time.”

The complexity is exactly what’s kept many banks on the sidelines. The appetite for multi-year, high-risk big bang replacements has largely evaporated, a change Temenos’s own executives are watching closely. “The large banks have now realized they can’t get on the AI train unless they really do modernize,” said Will Moroney, Temenos’s Chief Revenue Officer. The conversation has moved from wholesale replacement to progressive modernization, introducing new capabilities for deposits or lending while the legacy platform continues to run alongside, then migrating product by product.

Weiss sees AI reshaping the economics of that journey in ways that weren’t available when Regions started. Had the tools existed at the outset, he estimates the project could have been completed with roughly 30% less time and cost, a significant reduction, and one he believes will lower the barrier for other institutions considering similar moves. The areas where AI would have made the biggest difference: data management, data migration, integration, and testing. “These are all areas where generative AI can play a very strong role,” he said.

Regions has also been developing its own AI tools including Cash Flow IQ and Client IQ, but hasn’t fully deployed them yet. Governance, model validation, and the distance between demonstrated functionality and production readiness are all factors. “There’s a long way to go from demonstrated functionality to bringing it in house with model validation and everything else,” Weiss said. “It’s an exciting development and one that we’ll track through an appropriate governance process.”

Temenos has been focused on embedding AI directly into the platform rather than layering it on top — building “less but better,” with a deliberate narrowing of focus to use cases with broad impact across the client base. The FCM AI Agent, already live at a Tier 1 bank for sanctions screening, started at 5% of traffic and has been gradually expanded as the institution built organizational confidence alongside technical confidence.

Technical readiness first, organizational readiness alongside is a sequencing Weiss recognizes from the transformation playbook. The change management dimension of a core replacement is as demanding as the engineering dimension, and it extends well beyond the technology team. “One of the signatures of a core transformation is there’s a huge number of moving parts and pieces, none of which individually are particularly complex, but all those gears have to fit together in just the right way,” said a Temenos spokesperson.

For Regions, the competitive logic is straightforward. Being among the first large US banks to complete a move to a modern core creates flexibility that legacy-bound competitors won’t have. “We have a customer-centric culture,” Weiss said, “and what we’re doing is empowering our bankers with technology to serve our clients.”