Senior Staff Backend Engineer

Open 24d posting dated last week

Summary

Senior Staff Backend Engineer at Coupang designing and optimizing real-time e-commerce fulfillment systems that process millions of orders daily using Kotlin, Java, and optimization solvers.

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.

Show

What this application asks

greenhouse

First Name, Last Name, Email, Phone, Resume/CV, Cover Letter, Location

LinkedIn Profile optional
Coupang Corporation or its affiliates and subsidiaries* (collectively referred to as “Coupang”) does not collect or use any personal information other than the types of information specified in this Consent. Such information is collected and used as per the applicable law including the extant Digital Personal Data and Protection Act, 2023. (“Data Protection Act”) Please ensure that your resume does not include any personal information other than the types specified in this Consent. choose one
1. What is your nationality? choose one
2. Do you require a visa to legally work in India? choose one
1. (Required) By submitting your resume, you consent to the required collection and use, required provision, and consignment as set forth in our Privacy Policy(https://privacy.coupang.com/en/land/jobs/). choose one
2. (Optional) Name, contact information, email address, nationality, educational background, work experience, qualifications, national merit status (for special hiring program applicants only), relative’s name/relationship/team and application history are collected and used on an ongoing basis for recruitment purposes and may be provided to any of our affiliates and subsidiaries*, other than the company to which you originally applied, for the purpose of reviewing and conducting recruitment for similar positions. Personal information collected and provided will be retained for the duration of the year-round recruitment retention period defined in the Privacy Policy. You may refuse to provide consent, but such refusal may prevent you from applying. choose one
3. (Optional) Recordings of the interview process and transcriptions of interview audio maybe collected and used for the following purposes: i) to record the interview process, ii) to transcribe and document interview audio, iii) to summarize interview results, iv) to verify the interview process and evaluation results, v) to improve the hiring procedures, vi) to check candidate fit for other open positions, vii) to review past interview records. Collected personal information are retained for 4 years from the notification of hiring result, and then deleted. You may refuse to provide this consent, and refusal will not affect the recruitment process. choose one
4. (Optional) Coupang affiliate or subsidiary company* will send recruitment notifications through the agreed modes of communication, such as phone, email, and SMS using the contact information obtained with your consent. choose one
5. (Optional) I consent to reference checks on me within the following scope: Additional reference checks can be done on applicants who applied for a job at Coupang and passed on-site interviews, and Coupang arranges means to conduct reference checks. choose one
1. I understand that working with Relatives in the Coupang group of companies (collectively, the "Coupang Group") -- where they can influence each other’s work -- can potentially create conflicts of interest. Therefore, such a situation requires prior approval from the People Operations. In view of the above, I hereby confirm that I DO NOT have any Relatives working in any company within the Coupang Group or serving on the Board of Directors of any company within the Coupang Group; choose one
- Name of Relative(s): optional
- Relationship: optional
- Working Org/Team: optional
1. Are you currently, or have you been a government official, public servant, or employee of a public institution who may be subject to post‑employment or reemployment restrictions under applicable laws or regulations? choose one
2. Do you acknowledge and agree that where required under applicable laws or regulations: choose one · optional
[For more information] choose one
[Document Policy] choose one

Summary

What this application asks