Tandem Developer (Contract) - Cards andamp; BankingLocation: London (2-3 days onsite)Contract Duration: Until 31 December 2026Engagement: PAYE via Umbrella onlySecurity: BPSS eligibility requiredRole OverviewWe are seeking an experienced Tandem Developer to join a technology team delivering mission-critical banking and card payment solutions. This role focuses on the Cards domain, working within a high-availability environment supporting large-scale transaction processing systems.You will be responsible for developing, enhancing, and supporting HP NonStop (Tandem) applications that underpin card authorization, settlement, and payment processing platforms.Key ResponsibilitiesDesign, develop, and maintain applications on the HP NonStop (Tandem) platformDevelop and support solutions using TACL, Cobol, C, and GuardianDeliver and enhance card transaction processing, authorization, and settlement systemsIntegrate with core banking platforms, payment gateways, and downstream systemsPerform system analysis, troubleshooting, and performance tuning in high-volume environmentsEnsure compliance with PCI DSS, security, and regulatory standardsProvide L2/L3 production support for critical card and banking applicationsCollaborate with business analysts, engineers, and stakeholders to deliver scalable solutionsRequired Skills andamp; ExperienceStrong hands-on experience with HP NonStop (Tandem) systemsProficiency in TACL, Cobol, C, Guardian, and Enscribe/NonStop SQLSolid understanding of ISO