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AS400 Modernization Case Study: 20,000+ Transactions Automated Without Replacing the Legacy Core

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While many companies rush to modernize everything from scratch, some of the biggest players in Latin America are proving that legacy doesn't mean outdated →€” it means reliable. And with the right tech partner, legacy can become smart.

This is the story of how one of the largest financial institutions in LATAM tackled a major bottleneck in their card payment processing system by integrating cloud-native automation with their existing iSeries platform.

The Challenge: 20,000+ Unresolved Rejections

In the world of card payment processing, rejected transactions are more than just noise →€” they're a blocker for cash flow, reporting, and trust. This institution manages card payments (debit, credit, QR, and digital wallets) for thousands of merchants through its Acquiring Core running on FISERV.

But the process to handle funding rejections was completely manual. Six people were managing tens of thousands of rejections every month. That led to:

The Mission: Automate 95% of Manual Rejections

The goal was clear →€” automate the mass rejection handling process using FISERV's external Funding Rejects API, reducing manual intervention by at least 95%. But instead of replacing their iSeries core, they decided to augment it.

The Solution: Marrying iSeries with AWS Cloud

Architecture Overview

The entire flow allowed seamless, scalable, and traceable automation →€” without disrupting the legacy platform.

Results Delivered

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Over 20,000 transactions now processed efficiently and on time
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95% reduction in manual work
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Faster response times for merchant support
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Full traceability and scalability

Legacy Is Not Dead. It's Just Waiting to Be Reinvented.

If you're still running on AS400 or iSeries, you're not alone →€” and you're not outdated. You just need the right strategy to modernize without rewriting everything. At Aztia, we specialize in unlocking value from legacy systems through smart integrations and cloud-native extensions.

Still running on AS400?

See how we can help you modernize without replacing what already works.

Talk to our AS400 team →†’