Software Engineer III

CSI•Valparaiso, IN

About The Position

We are seeking a highly skilled Software Engineer with extensive experience in ACI Postilion Realtime SDK, payment network integrations, and transaction switching. The ideal candidate will be responsible for designing, developing, and supporting high-volume payment processing solutions that integrate with card networks, EFT networks, core banking systems, and third-party payment services. This role requires strong expertise in electronic payments, ISO 8583 messaging, transaction routing, authorization processing, network connectivity, and end-to-end payment transaction lifecycle management.

Requirements

5+ years of software development experience.
5+ years of hands-on experience with ACI Postilion.
Strong experience developing solutions using Postilion Realtime SDK.
Experience supporting production payment switching environments.
Proven experience integrating payment networks and third-party processors.
Strong understanding of ISO 8583 transaction messaging.
Experience with ATM transaction processing
Experience with POS transaction processing
Experience with Debit and credit card payment systems
Experience with Authorization and settlement flows
Programming experience in Java.
Proficiency with SQL and relational databases.
Strong TCP/IP networking knowledge.
Experience with REST APIs, Web Services, and socket-based integrations.
Familiarity with Windows and Linux server administration.
Experience integrating with Visa, Mastercard, Pulse, NYCE, STAR, or similar networks.
Knowledge of acquiring and issuing transaction flows.
Understanding of network certification processes.
Experience troubleshooting network connectivity and transaction routing issues.
Familiarity with payment settlement and reconciliation processes.
Strong analytical and troubleshooting capabilities.
Excellent verbal and written communication skills.
Ability to work effectively in mission-critical production environments.
Strong understanding of payment ecosystems and transaction processing.
Ability to mentor junior engineers and lead technical initiatives.
Self-motivated with a strong focus on quality and operational excellence.
Applicants must be authorized to work in the United States without the need for sponsorship now or in the future.

Nice To Haves

Experience with Postilion Office, Postilion Portal, Postilion Office Recon product.
Experience with HSMs such as Atalla AKB, Thales, or Entrust.
Knowledge of EMV, contactless, tokenization, and digital wallets.
Knowledge of Visa, Mastercard SMS, or similar payment processing platforms.
Experience working in Agile/Scrum environments.

Responsibilities

Design, develop, and maintain custom applications using Postilion Realtime SDK.
Develop new nodes using Rest API, routing logic, and authorization modules within the Postilion platform.
Customize and support Postilion transaction workflows to meet business and network requirements.
Develop interfaces between Postilion and external systems, including issuer hosts, fraud systems, and payment gateways.
Participate in system enhancements, upgrades, and migrations.
Design and implement integrations with payment networks, including Visa, Mastercard, Pulse, NYCE, STAR.
Support network certifications and transaction testing activities.
Implement and troubleshoot network management messages and routing configurations.
Analyze network specifications and translate them into technical solutions.
Configure and support ATM, POS, debit card, credit card, and digital payment transaction processing.
Design and maintain authorization, stand-in processing, routing, settlement, and reconciliation functions.
Investigate and resolve transaction failures and network communication issues.
Optimize transaction performance and throughput for high-volume payment environments.
Develop and troubleshoot ISO 8583 message parsing, transformation, and routing.
Map transaction messages between payment networks and internal systems.
Analyze message logs and perform transaction-level troubleshooting.
Support custom message formats and network-specific extensions.
Monitor production transaction flows and switch performance.
Provide Level 2/Level 3 support for payment processing applications.
Conduct root cause analysis and implement corrective actions for incidents.
Participate in on-call support rotations and critical production deployments.
Ensure system uptime, resilience, and regulatory compliance.
Support PCI DSS compliance initiatives.
Implement secure transaction processing practices.
Work with HSM integrations for PIN and key management.
Ensure adherence to payment industry security standards.