Freelance Backend Engineer—Payments & Ordering Platform

Openkrill; United States; Remote; USD 160,000 - 240,000; Full time

Job summary

Sunday is building the fastest, simplest way to pay in restaurants. We are seeking two senior back-end engineers to grow the Billing & Ordering Platform, focusing on reliability, scalability, and maintainability of invoices and orders.

Join a highly autonomous team, work on Kotlin/Java, Spring Boot, and distributed systems, with observability tooling and a path to impact the architecture while delivering real-world payment experiences.

Qualifications

• 7+ years of professional software development experience.
• Strong JVM experience with Kotlin or modern Java.
• Professional experience with Spring Boot.
• Experience designing and operating distributed systems in production.
• Strong API and integration design, contracts evolution.
• Ability to own a topic end to end including monitoring and ops.
• Professional English for team rituals and documentation.

Responsibilities

• Design, develop, and maintain back-end services in Kotlin/Java on the JVM.
• Unify boundaries between billing and ordering.
• Evolve REST and gRPC APIs with versioning and contracts.
• Build reusable models for invoice and order flows.
• Improve reliability of distributed flows with idempotency, retries, deduplication, reconciliation.
• Enhance production observability with metrics, logs, traces, dashboards, alerts.
• Diagnose end-to-end issues across services and integrations.
• Contribute to architecture discussions and ADRs.
• Collaborate with product, POS, loyalty, and partners to improve platform.
• Occasionally contribute to CI/CD and infrastructure code.
• Share knowledge and build reusable patterns as team grows.

Skills

Kotlin

Java

Spring Boot

Distributed systems

API design

English proficiency

Tools

Kafka

gRPC

Datadog

PostgreSQL

CI/CD

Job description

Sunday is building the fastest, simplest way to pay in restaurants. We are seeking two senior back-end engineers to grow the Billing & Ordering Platform, focusing on reliability, scalability, and maintainability of invoices and orders.

Join a highly autonomous team, work on Kotlin/Java, Spring Boot, and distributed systems, with observability tooling and a path to impact the architecture while delivering real-world payment experiences.