Senior Backend Engineer – Credit Card Payments

iwoca

. Design and build the payments platform behind iwoca’s business credit card .

Posted 10/27/2026full-timeLondon • United KingdomSenior💰 £100,000 - £120,000 per yearWebsite

Core Competencies

Role fit

Core Competencies

Use this summary to align your resume positioning with the role.

Demonstrates expertise in designing and building highly available payment systems, with a focus on backend services, transaction monitoring, and compliance with card scheme rules. Proficient in object-oriented programming, microservices architecture, and database design, particularly in PostgreSQL.

Highest-signal resume keywords

Payment Systems DesignBackend Services DevelopmentMicroservices ArchitectureTransaction MonitoringPostgreSQL Database Design

ATS Keywords

Tailor your resume

Applicant Tracking System Keywords

Tip: use these terms in your resume and cover letter to boost ATS matches.

Hard Skills

Object-Oriented ProgrammingREST API DevelopmentAsynchronous MessagingTransaction TracingPayment AuthorisationFraud DetectionDatabase Schema DesignAutomated TestingAI Workflow IntegrationProduction Issue Resolution

Soft Skills

Clear CommunicationAdaptability

Tools & Technologies

PostgreSQLPayment PlatformsMicroservicesAI ToolsAutomated Testing Frameworks

Industry Keywords

Card Scheme RulesTransaction MonitoringFinancial Crime RiskClearing SystemsReconciliation

Tech Stack

Tools & technologies

MicroservicesPostgresPython

About the role

Key responsibilities & impact

Design and build the payments platform behind iwoca’s business credit card
Own backend services and projects end to end
Shape platform architecture with the principal engineer
Define service boundaries and how authorisation, rewards, and transaction monitoring fit together
Work closely with product to decide what the team builds and how
Help take the card payments platform into production
Scale payments within card scheme rules and regulatory requirements
Extend real-time payment authorisation services
Place holds on available credit in the ledger and apply account, merchant category code, and spend-limit checks
Build transaction monitoring for fraud and financial-crime risk
Extend cashback rewards services
Design sandbox tests for edge cases and failures across the card transaction lifecycle
Move the card platform onto iwoca’s own ledger and infrastructure with minimal downtime
Resolve production issues after go-live
Collaborate with ledger, customer product, and fraud teams

Requirements

What you’ll need

Experience designing and running highly available, low-latency payment systems in production, ideally on the issuing side
Experience with card authorisation and clearing
Ability to trace transactions from the terminal through the acquirer and card scheme to the issuer
Experience using response codes to diagnose declined transactions
Deep expertise in at least one object-oriented language
Experience writing and running backend services
Experience building microservices, REST APIs, and asynchronous messaging with queues or topics
Experience designing database schemas, ideally in PostgreSQL
Experience building agentic workflows or using AI to scale engineering output
Ability to judge when to use AI and verify its output before production
Clear, direct, and concise written and spoken communication
Ability to adapt technical detail to the audience
Bonus: experience with ledgers, reconciliation, or clearing systems
Bonus: automated testing for payment systems, ideally test-first
Bonus: production Python experience

Benefits

Comp & perks

Flexible working hours
Medical insurance from Vitality, including discounted gym membership
Private GP service for you, your partner, and your dependents
25 days’ holiday per year
Extra day off for your birthday
Option to buy or sell an additional five days of annual leave
Unlimited unpaid leave
One-month, fully paid sabbatical after four years
External counselling and therapy sessions
3% pension contributions on total earnings
Employee equity incentive scheme
Generous parental leave
Nursery tax benefit scheme
Electric car scheme
Cycle to work scheme
Two company retreats a year
Learning and development budget
Company-wide talks with internal and external speakers
Access to learning platforms like Treehouse
Offices with drinks and snacks
Events and community-led groups, including running groups, padel, ping-pong and pool competitions