PNC cut nearly 600 apps during its $11.5 billion acquisition of BBVA, which closed in June. That’s roughly one app for each BBVA branch.

Chief Executive Officer Bill Demchak said PNC retained only two BBVA apps when all was said and done. The $553.5 billion PNC converted approximately 2.6 million customers, 9,000 employees and nearly 600 branches across seven states as part of the deal, Demchak said during the bank’s Oct. 15 earnings call.

“They had 600. We run the whole bank on 300,” the CEO said. “They’re so much smaller, yet they had twice as many apps.”

Demchak credited the bank’s use of application programming interfaces (APIs) with PNC’s ability to maintain a small app footprint. For instance, if an application needs a checking account balance, rather than writing a full application to find the checking account balance off the core ledger, PNC simply uses an API to call up the balance.

“Once you start using API-based programs, it’s almost a click and drag, right? You don’t have to recreate functionality across multiple applications,” Demchak said. “You can simply bring in whatever functionality you need from a library of API.”

PNC reported earnings of $1.5 billion, with revenue of $ 5.2 billion, up $4.3 billion from third quarter 2020. The Pittsburg, Penn. bank does not break out technology spend, but expense categories that might cover tech spend include “Equipment,” which was $355 million, and “Other,” which was $895 million for the third quarter; both were up slightly from Q3 2020.

Though the expense report did not break out technology investments, Demchak credited “sustained investments in technology,” along with employee dedication, with its ability to convert nearly 600 BBVA branches to PNC locations this year.

“The technology, look, it worked,” Demchak said. “We had at the margin, some confusion with retail clients on password resets and some other things, but the basic technology moving it overturned it on, it all worked.

“It’s this just phenomenal effort by our team and validates the investment we’ve made over the years.”

In particular, the CEO credited the bank’s use of a central data lake and a cloud-native approach. Rather than applications holding their own data, they call data via an API from the data lake, Demchak explained.

“It just makes it very easy to move data and you onboard a new client, it’s not much different than is if we just got a couple of million new clients overnight,” he said. “I make it sound very easy and all my technologists are ripping their hair off right now. But that’s what we did, and it worked.”

Demchak also credited PNC’s culture of having technologists work “side by side in an agile team working with their business partners to develop product, and importantly, to execute the conversion, which we did.”

Finally, Demchak highlighted the bank’s recent integration of Akoya Data Access Network, another API-enabled play. PNC is also giving customers the choice to share data with third-party applications, he said.

“The integration is going to allow millions of our customers, if they choose to do so, to safely share their financial information with fintechs and data aggregators,” Demchak said. “It’s an important step in our efforts to help our customers protect their data.”

PNC [NYSE: PNC] shares were trading at $200.84 as of 4:23 p.m., up 0.8% as of market open.