Case Study

Payment Gateway for Global Scale

Multi-year gateway engineering, compliance, and platform modernisation for a world-leading payments provider.

Client overview

The client is a large international financial technology company listed on major US stock indexes. The organisation provides payment technology and services to merchants, issuers, and consumers in more than 100 countries and processes tens of billions of transactions annually.

Espeo Software joined the engagement through a payment gateway platform that became part of the client’s broader payments ecosystem following a strategic acquisition.

Project details

Legacy Platform and Regulatory Pressure

The gateway relied on legacy technology, including Flash-based interfaces, and faced mounting demands around PSD2, Strong Customer Authentication (SCA), and PCI-DSS. Peak events in gaming stretched infrastructure, while merchant integrations depended on outdated SFTP workflows.

End-to-End Modernisation

The programme set out to modernise the gateway: migrate Flash to React, build recurring payments and Buy Now Pay Later (BNPL) modules, harden security after external audits, and ensure peak-load reliability – all while maintaining compliance across live merchant traffic.

years programme span

modules shipped

specialists

0 +

Modernise the gateway from Flash to React

Build recurring payments and BNPL modules

Achieve PCI-DSS and PSD2/SCA compliance

Harden security after external code audits

Ensure peak-load reliability for gaming

How we did it

Discovery & architecture planning

We assessed the legacy gateway, mapped dependencies across payments, merchant, and compliance domains, and defined a modernisation roadmap spanning multiple years – prioritising modules by regulatory urgency and merchant impact.

Frontend modernisation

We migrated critical interfaces from Flash to React, working alongside the Client. The transition covered architecture planning, component builds, and iterative rollouts across merchant-facing services.

Payments module development

We built the recurring payments module, BNPL and instalment features for POS terminals, and merchant integration APIs – replacing SFTP-based workflows with secure HTTPS endpoints for faster, more reliable merchant onboarding.

Security, compliance & certification

We remediated findings from external security audits, implemented PCI DSS controls across card flows, and delivered PSD2/SCA logic.

Ongoing operation

The platform was stabilised for extreme traffic events typical for gaming and ticketing environments. The team created reusable operational playbooks for high-load scenarios and supported the gateway through ongoing change requests, protocol upgrades, and network modernisation.

Tech stack & team composition

Team Lead

Backend Engineers (Java)

Frontend Engineers (React)

QA Engineers

DevOps Engineers

Results

Recurring payments

Module launched and maintained continuously since.

React migration

Legacy interfaces replaced across merchant-facing services.

Security hardened

Veracode findings remediated; PCI-DSS and PSD2 compliance achieved.

Peak-load reliability

Gateway stabilised for high-traffic gaming and ticketing events.

Multi-year embedded team

Engineers worked alongside client squads for over seven years.

Espeo's team became an extension of our own engineering function.

Senior Technology Stakeholder

Embedded engineers worked alongside client squads for years: handling gateway development, compliance, and peak-event reliability.

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