Custom Payment Processor

Overview

A custom payment processor is the deepest form of payments ownership available to a business. Instead of integrating with a third-party gateway or renting acquiring capacity from a partner, you commission an independent system that authorises, clears, settles and reports on transactions under rules you control. Pay Engineers builds these processors for fintechs, digital banks, PSPs and large platforms that have outgrown off-the-shelf providers or that need commercial and regulatory flexibility those providers cannot offer.

The result is not a proof of concept. It is a production system engineered to handle real transaction volumes, connect to multiple card schemes and local rails, and operate under the scrutiny of card networks, regulators and your own risk committee. Every component, from the authorisation engine to the settlement ledger, is designed around your specific corridors, currencies and business model rather than adapted from a generic template built for someone else.

We treat a processor build as a long-term engineering relationship, not a one-off delivery. The architecture decisions made in the first weeks of discovery determine how easily you will add new schemes, currencies and merchant segments three years from now, so we spend real time understanding your roadmap before committing to a design.

Who This Is For

This service is built for organisations that have reached the limits of buying payments capability from someone else. Typical clients include:

• Fintechs and digital banks that need proprietary rails to differentiate on pricing, speed or product
• Acquirers and PSPs replacing legacy or vendor-locked processing cores that constrain their commercial model
• Platforms and marketplaces whose transaction economics no longer work with generic, off-the-shelf processors
• Regulated institutions such as EMIs, PIs and banks that must demonstrate direct technical control over payment flows to regulators and auditors

If your business is currently paying per-transaction margin to a processor whose roadmap you cannot influence, or if you are being told a feature you need is "not supported" by a vendor, this is very likely the right stage to consider building your own core.

What You Get

Every engagement is scoped around a concrete set of deliverables so that your stakeholders know exactly what production readiness looks like before the project starts:

• Architecture blueprint mapping authorisation, clearing, settlement and reporting flows to your specific business rules and corridors
• Core processor modules covering authorisation routing, transaction lifecycle management, fee and pricing engines, and merchant onboarding
• Admin and operations consoles for support, finance and risk teams to manage the platform on a daily basis without engineering intervention
• A dedicated sandbox environment for scheme and partner certification testing, isolated from production
• Runbooks, architecture documentation and a structured handover to your internal engineering team

Technical Approach

The processor is built on a stack chosen for throughput, consistency and operability at scale: Laravel and Go services form the API and orchestration layers, Java is used where deterministic performance and mature scheme SDK support are required, PostgreSQL acts as the system of record for ledgers and transaction state, and Redis handles velocity checks, idempotency and caching. Kubernetes on AWS gives you elastic, multi-region deployment with the resilience card schemes expect from certified processors.

Multi-rail authorisation and clearing logic is built so that new acquiring corridors, local payment methods or scheme connections can be added without re-architecting the core. Fee and pricing engines are fully configurable, supporting blended, interchange-plus and fully custom merchant pricing models, so commercial teams can launch new pricing without waiting on an engineering release cycle.

Merchant onboarding and KYC workflows are wired directly into the processor so that risk and compliance decisions happen at the point of provisioning, not as a bolt-on after the fact. Settlement, reconciliation and reporting are treated as first-class citizens of the architecture from day one, because finance teams cannot operate on data that only becomes trustworthy weeks after go-live. Risk, velocity and scheme compliance hooks are embedded at the authorisation layer, giving you a single place to enforce policy across every acquiring relationship.

Delivery Process

We run processor builds as a disciplined, milestone-driven programme rather than an open-ended engagement:

• Discovery and corridor mapping to understand your markets, volumes, schemes and regulatory constraints in detail
• Architecture sign-off with your engineering, risk and compliance stakeholders before a single line of production code is written
• Agile build sprints delivering working increments of the processor, with continuous demos and structured feedback loops
• Partner and scheme certification support, including test scripts, evidence packs and remediation of any findings raised
• Production rollout with phased traffic migration, close monitoring and a clearly defined hypercare period

Outcomes and Benefits

Clients who complete a processor build with us typically see a fundamental shift in how their payments function operates commercially and technically:

• Full ownership of authorisation logic, pricing and merchant economics, with no vendor markup on every transaction processed
• Ability to launch new markets, currencies and payment methods on your own timeline rather than a vendor roadmap
• A processor architecture built to withstand PCI, scheme and regulatory audits from day one, not retrofitted later
• An internal engineering team fully equipped, through documentation and structured handover, to operate and extend the platform independently for years to come