SME Card Issuing Authorization & Rewards Backend Engineer — Hybrid, London, United Kingdom

Overview

Own production backend systems for a business credit-card issuing platform. Develop authorization and clearing services that make instant approve/decline decisions, reserve credit-ledger balances, inspect financial crime signals and calculate cashback rewards under payment network rules.

Requirements

• Experience designing and operating highly available, low-latency payment systems in production, ideally in card issuing.
• Deep understanding of card authorization and clearing through acquirer, card network and issuer, including decline codes and transaction troubleshooting.
• Strong object-oriented backend engineering and ownership of production services.
• Microservice and REST API design, asynchronous messaging and relational database schemas, preferably PostgreSQL.
• Practical experience with agentic or AI-assisted engineering workflows and independent review of model outputs.
• Ability to communicate clearly with engineering, product and risk stakeholders.
• Ledger/reconciliation/clearing systems, test-first automated payment testing and production Python are beneficial rather than mandatory.

Responsibilities

• Design and maintain real-time business card payment authorization and decline services.
• Apply credit limits, merchant category restrictions and account-status controls during transaction approval.
• Build payment fraud and financial-crime checks into the card issuing transaction flow.
• Operate cashback accrual and rewards payout services.
• Write resilient sandbox tests covering card network errors, declines and failed clearing.
• Migrate services safely to in-house ledgers while maintaining uptime.
• Own service architecture, production incidents and delivery with product and principal engineering.

Conditions

• Full-time hybrid position based in London, United Kingdom.