Senior Backend Engineer: POS & Commerce Integrations

On; City Of London; On-site; GBP 90,000 - 130,000; Full time

Job summary

On is building a future-ready POS ecosystem. We seek a backend/ integration engineer to design scalable services powering POS integrations across ERP, eCom, CRM, inventory, and loyalty.

You’ll implement REST/GraphQL APIs, real-time data flows, and secure auth patterns while embracing a cloud-native, event-driven architecture. You’ll work on testing, monitoring, and collaboration with frontend, product, and vendor teams to shape the composable commerce stack.

Qualifications

• Strong backend engineering experience with modern technologies (Node.js/TypeScript or similar).
• Proven track record integrating APIs across commerce, ERP, OMS, or CRM domains.
• Familiar with headless commerce, microservices, and composable architecture principles.
• Experience with message brokers (Kafka) and asynchronous data processing.
• Solid understanding of databases (PostgreSQL) and IaC tools (Terraform).
• Skilled in designing, scaling, and monitoring cloud-native services (AWS, GCP, or Azure).
• Familiarity with OAuth2, token-based authentication, and secure service design.
• Strong debugging and telemetry skills: logs, traces, metrics, and real-time alerting.

Responsibilities

• Backend & integration engineering: design, build, and scale backend services powering POS integrations across ERP, eCom, CRM, inventory, and loyalty.
• Architecture & resilience: build cloud-native, event-driven patterns with scalable messaging (Kafka) and serverless workflows.
• Testing & automation: implement contract/load tests and data pipelines; contribute to CI/CD and release confidence.
• Collaboration & strategy: align integration design with platform capabilities; influence vendor evaluations and roadmaps.

Skills

Backend engineering

API integration

Headless commerce

Kafka

PostgreSQL

Terraform

Cloud platforms

OAuth2

Telemetry

Tools

Terraform

NewRelic

OAuth2

Job description

On is building a future-ready POS ecosystem. We seek a backend/ integration engineer to design scalable services powering POS integrations across ERP, eCom, CRM, inventory, and loyalty.

You’ll implement REST/GraphQL APIs, real-time data flows, and secure auth patterns while embracing a cloud-native, event-driven architecture. You’ll work on testing, monitoring, and collaboration with frontend, product, and vendor teams to shape the composable commerce stack.