Staff Backend Engineer

Senior Staff Backend Engineer

Coupang

Company Introduction   We exist to wow our customers. We know we’re doing the right thing when we hear our customers say, “How did we ever live without Coupang?” Born out of an obsession to make shopping, eating, and living easier than ever, we’re collectively disrupting the multi-billion-dollar e-commerce industry from the ground up. We are one of the fastest-growing e-commerce companies that established an unparalleled reputation for being a dominant and reliable force in South Korean commerce.    We are proud to have the best of both worlds — a startup culture with the resources of a large global public company. This fuels us to continue our growth and launch new services at the speed we have been since our inception. We are all entrepreneurs surrounded by opportunities to drive new initiatives and innovations. At our core, we are bold and ambitious people that like to get our hands dirty and make a hands-on impact. At Coupang, you will see yourself, your colleagues, your team, and the company grow every day.   Our mission to build the future of commerce is real. We push the boundaries of what’s possible to solve problems and break traditional tradeoffs. Join Coupang now to create an epic experience in this always-on, high-tech, and hyper-connected world.     Role Overview We're looking for a Senior Staff Engineer to lead the technical direction of MyCoupang, Coupang's post-purchase customer experience platform. Every order tracking, delivery, return, payment, and support interaction for tens of millions of active customers across Korea and Taiwan flows through this system.  MyCoupang operates at significant scale: ~34,000 requests per second, ~2.4 billion requests daily, and ~16 billion weekly, served by 700+ production pods with a 9x daily traffic swing that must be absorbed seamlessly. The platform delivers P95 latency under 500ms, P99 under 1 second, and maintains a 0.002% error rate. Built on Kotlin (backend), TypeScript with server-side rendering and ReactJS (frontend), the system spans a dual-service architecture with 100+ page routes and 30+ business domains including Orders, Payments, Delivery, Cancel/ Return/Exchange, WOW Membership, Travel, and Contact Center. The team ships 100+ features monthly, supports multi-market business logic across KR and TW (each with region-specific compliance, internationalization, and payment methods), and enforces security through a 4-phase authorization pipeline. This is a complex, high-stakes environment where architectural decisions have immediate customer impact. What You Will Do  In this role, you will own the most critical technical challenges on the platform: designing multi-market abstractions that scale to new regions, driving the system toward 99.99% availability, leading disaster recovery readiness and capacity planning across the full production fleet, and defining the long-term architecture for a platform that must reliably serve billions of requests weekly while continuing to evolve. You will directly influence customer retention and satisfaction metrics for every Coupang post-purchase interaction, set the engineering bar for the team, and shape the technical strategy for one of Coupang's most customer-facing systems. Basic Qualifications  * Minimum 12 years of experience working on software design and development in Java. * Hands-on experience with designing, building, and deploying scalable, high available systems * Experience with high-throughput, low-latency systems handling millions of requests * Experience with event-driven architectures using Kafka or similar messaging systems * Strong problem-solving skills and ability to debug complex distributed systems * Excellent collaboration skills to work with cross-functional teams (Product, CS, Logistics, Payment) Preferred Qualifications   * Backend development (Java, Kotlin, or similar JVM languages preferred) * RESTful API design and implementation * Database design and optimization (MySQL, * Aurora)Message queue systems * (Kafka)Workflow engines (Activiti BPMN, Temporal) * Monitoring and alerting (Grafana, CloudWatch) * Version control * (Git)CI/CD tools (CircleCI or similar   Type of work model  * Hybrid Details to consider  * Those eligible for employment protection (recipients of veteran’s benefits, the disabled, etc.) may receive preferential treatment for employment in accordance with applicable laws.    Privacy Notice   * Your personal information will be collected and managed by Coupang as stated in the Application Privacy Notice located below. https://privacy.coupang.com/en/land/jobs/

Senior Staff Backend Engineer

Coupang

Company Introduction   We exist to wow our customers. We know we’re doing the right thing when we hear our customers say, “How did I ever live without Coupang?” Born out of an obsession to make shopping, eating, and living easier than ever, we’re collectively disrupting the multi-billion-dollar e-commerce industry from the ground up. We are one of the fastest-growing e-commerce companies that established an unparalleled reputation for being a dominant and reliable force in South Korean commerce.    We are proud to have the best of both worlds — a startup culture with the resources of a large global public company. This fuels us to continue our growth and launch new services at the speed we have been since our inception. We are all entrepreneurs surrounded by opportunities to drive new initiatives and innovations. At our core, we are bold and ambitious people that like to get our hands dirty and make a hands-on impact. At Coupang, you will see yourself, your colleagues, your team, and the company grow every day.   Our mission to build the future of commerce is real. We push the boundaries of what’s possible to solve problems and break traditional trade-offs. Join Coupang now to create an epic experience in this always-on, high-tech, and hyper-connected world.     Role Overview Fulfilment Optimization (FO) owns the systems that decide how every Coupang order is planned, distributed, and fulfilled. Our Tier-1 services sit on the critical path of Coupang's ecommerce order flow — processing every order in real time across Korea and Taiwan. We operate multiple interconnected platform components: -Business Engine — Core order planning and distribution orchestrator (Kotlin/Spring Boot). Runs 5 distinct pipelines (Domestic, Cross-Market, 3PL, PDD, Replan) using a hexagonal architecture with pluggable processors, pruners, and manifest-based orchestration. -Planner Solver — Mixed-Integer Programming (MIP) optimization engine (Python/CPLEX) that minimizes total fulfilment cost across inventory, capacity, network, and delivery-promise constraints with sub-second latency requirements. -Network Manager — Manages fulfilment network topology, transportation cost, FC capacity, middle-mile logistics, and cross-FC consolidation (CFCC) across 90+ REST/gRPC endpoints. -FO Inventory — Real-time inventory availability, allocation, SKU management, and event-driven sync across multiple upstream sources (Kafka, Cassandra, Elasticsearch, Redis). -WMS Fulfilment — Order distribution, inventory allocation, fulfilment centre orchestration, shipment, delivery, and outbound management (Java/Spring, 138+ domain subpackages, Drools rules engine). -Online Simulation — Real-time simulation platform for testing planning changes against production-like order streams. -FO Workflows — Temporal-based workflow orchestration for long-running fulfilment processes. The Role We are looking for a Senior Staff Engineer who can operate across deep implementation and broad architecture. You will set the technical direction for Tier-1 fulfilment systems, write and review production code, design systems that scale under heavy ecommerce traffic, and raise the engineering bar across the organization. The engineer in this role will directly influence how millions of orders are fulfilled every day. Every architectural decision — solver latency, pruning strategy, network cost calculation, inventory allocation algorithm impacts customer delivery promise, fulfilment cost, and operational efficiency across Coupang's entire ecommerce platform in Korea and Taiwan. This is a rare opportunity to work at the intersection of large-scale distributed systems, real-time optimization, and ecommerce fulfilment — with direct, measurable business impact. What You Will Do  -Design and build scalable, reliable Tier-1 services for order planning, fulfilment optimization, inventory allocation, and network cost management — systems that process every Coupang order in real time. -Own architecture across distributed systems involving gRPC service meshes, Kafka event pipelines, CPLEX optimization solvers, multi-layer caching (Redis, S3-backed Loadable Stores), and multi-region deployments. -Write production code in Kotlin and Java and set the bar for correctness, performance, and operational safety across the team. -Lead design and code reviews — identify correctness issues, scalability risks, and operational gaps in systems handling latency-sensitive order flows (sub-second solver deadlines, P99 monitoring with 3-5s alert thresholds). -Drive reliability for mission-critical services — circuit breakers, graceful degradation (hard/soft pruners with fallback), observability, and incident prevention. -Partner with Product, Data Science, and Operations to translate fulfilment optimization goals into technical execution — PDD rationalization, CFCC (Cross-FC Consolidation), CFlow transport planning, inventory group management, and solver model improvements. -Mentor engineers and create durable technical mechanisms (pipeline patterns, adapter abstractions, feature flag discipline) that scale beyond individual projects   Basic Qualifications -Proven experience designing and operating high-scale distributed systems with strict latency and reliability requirements -Excellent hands-on coding ability in Kotlin or Java (backend systems at scale) -Deep understanding of system design — API design, concurrency, data modelling, caching strategies, messaging, service-to-service communication (gRPC, REST) -Strong code review skills — ability to identify subtle correctness, performance, and reliability issues in complex codebases -Experience with production-grade systems handling high QPS, large data volumes, or Tier-1 SLAs -Experience with event-driven architectures using Kafka at scale -Experience with multi-region systems — region-specific routing, data isolation, cross-border fulfilment -Experience with resilience engineering — circuit breakers, retry strategies, load testing, capacity planning, graceful degradation patterns -Track record of technical leadership — setting architecture direction, driving cross-team alignment, mentoring senior engineers   Preferred Qualifications -Experience in ecommerce, fulfilment, supply chain, logistics, inventory, order management, or planning systems -Experience with optimization systems — solvers (CPLEX, OR-Tools), decision engines, constraint programming, or data-science-integrated production systems -Experience with Agentic AI tools for development and code review — using AI-assisted coding agents (e.g., Cursor, Copilot, Devin, Claude Code) to accelerate development velocity, improve code review quality, and automate repetitive engineering tasks -Experience with Spec-Driven Development — defining system behaviour through specifications (OpenAPI/Swagger, Protocol Buffers, API-first design, contract-first development) before implementation, ensuring well-defined contracts between services   Type of work model * Hybrid Details to consider  * Those eligible for employment protection (recipients of veteran’s benefits, the disabled, etc.) may receive preferential treatment for employment in accordance with applicable laws.    Privacy Notice * Your personal information will be collected and managed by Coupang as stated in the Application Privacy Notice located below. https://privacy.coupang.com/en/land/jobs/

Staff Engineer - Backend (Post Purchase Experience)

Coupang

Company Introduction   We exist to wow our customers. We know we’re doing the right thing when we hear our customers say, “How did we ever live without Coupang?” Born out of an obsession to make shopping, eating, and living easier than ever, we’re collectively disrupting the multi-billion-dollar e-commerce industry from the ground up. We are one of the fastest-growing e-commerce companies that established an unparalleled reputation for being a dominant and reliable force in South Korean commerce.    We are proud to have the best of both worlds — a startup culture with the resources of a large global public company. This fuels us to continue our growth and launch new services at the speed we have been since our inception. We are all entrepreneurs surrounded by opportunities to drive new initiatives and innovations. At our core, we are bold and ambitious people that like to get our hands dirty and make a hands-on impact. At Coupang, you will see yourself, your colleagues, your team, and the company grow every day.   Our mission to build the future of commerce is real. We push the boundaries of what’s possible to solve problems and break traditional tradeoffs. Join Coupang now to create an epic experience in this always-on, high-tech, and hyper-connected world.     Role Overview  The C-Returns Platform team owns the end-to-end lifecycle of cancellations, returns, and exchanges for Coupang's e-commerce ecosystem. We process millions of post-purchase resolution requests through our customer facing Coupang App and CS/back-office channels, serving both Korea and Taiwan markets. Our platform is mission-critical infrastructure that directly impacts: * Customer satisfaction — making post-purchase resolution fast, transparent, and predictable * Inventory protection — minimizing inventory loss through structured collection logistics, QA inspections, and time-bound auto-withdrawal policies * Business agility — enabling rapid policy changes through event-driven architecture with visibility and adaptability What You Will Do  * Build and maintain Tier 1 & Tier 2 services that handle 500K+ requests/day across multiple microservices * Design and implement complex business workflows using Activiti BPMN and Temporal Cloud for orchestrating cancellations, returns, exchanges, and refunds * Integrate with 15+ upstream and downstream systems including Order, Shipment, Payments, Transport. * Implement policy-driven business logic that adapts to frequently changing cancellation, return, and refund rules   Basic Qualifications * 7+ years of backend software engineering experience * Strong proficiency in building distributed systems and microservices architecture * Experience with high-throughput, low-latency systems handling millions of requests * Experience with event-driven architectures using Kafka or similar messaging systems * Strong problem-solving skills and ability to debug complex distributed systems * Excellent collaboration skills to work with cross-functional teams (Product, CS, Logistics, Payment) Preferred Qualifications * Backend development (Java, Kotlin, or similar JVM languages preferred) * RESTful API design and implementation * Database design and optimization (MySQL, Aurora) * Message queue systems (Kafka) * Workflow engines (Activiti BPMN, Temporal) * Monitoring and alerting (Grafana, CloudWatch) * Version control (Git) * CI/CD tools (CircleCI or similar) Type of work model  * Hybrid / Onsite / Remote working  Our Hybrid work model: Coupang hybrid work model is designed to enable a culture of collaboration that acts a catalyst to enrich the experience of employees. Employees are required to work at least 3 days in the office per week, with the flexibility to work from home 2 days a week, depending on the role requirement. Some businesses may require more time in office due to nature of work.   Details to consider  * Those eligible for employment protection (recipients of veteran’s benefits, the disabled, etc.) may receive preferential treatment for employment in accordance with applicable laws.    Privacy Notice   * Your personal information will be collected and managed by Coupang as stated in the Application Privacy Notice located below. https://privacy.coupang.com/en/land/jobs/