Flex is hiring a Contract Implementation Engineer to support merchant onboarding and technical integrations. This role sits at the intersection of Support Engineering, Product, and Customer Success, focused on helping partners successfully implement and launch our APIs and checkout flows. You'll be in a hands-on, execution-oriented role ideal for someone who enjoys working directly with customers, debugging real-world integration issues, and shipping solutions quickly in a fast-moving startup environment.

What You'll Do

Support merchants during onboarding and implementation of our APIs and checkout solutions.
Troubleshoot integration issues related to APIs, webhooks, authentication, and payment flows.
Review and validate API requests/responses using tools like Postman and logs.
Assist merchants with setup across platforms, including custom integrations and e-commerce platforms.
Debug issues related to subscriptions, payments, webhooks, and data mismatches.
Partner closely with Support Engineering, Product, and Engineering to escalate bugs and unblock launches.
Help document common implementation patterns, FAQs, and known issues.
Occasionally assist with light data validation or configuration updates in internal tools.

What We're Looking For

2+ years of experience in an implementation, support engineering, or customer engineering role.
Comfortable working with REST APIs, JSON, and HTTP requests.
Experience using Postman or similar tools to test and debug APIs.
Familiarity with webhooks and asynchronous event flows.
Strong troubleshooting and problem-solving skills.
Clear, empathetic written communication for working directly with external partners.
Ability to work independently, prioritize tasks, and manage multiple implementations at once.
Experience in Shopify implementation.

Nice to Have

Experience supporting payment systems, subscriptions, or checkout flows.
Familiarity with Stripe, Shopify, or other e-commerce platforms.
Experience in a startup or high-growth environment.
Light SQL or data-debugging experience.
Previous experience working with customer-facing technical roles.

Technical Stack

REST APIs
JSON
Postman
Shopify
Stripe

Team & Environment

You’ll play a critical role in getting partners live and successful while working closely with a small, collaborative team. This role is ideal for someone who likes being close to real customer problems and seeing the direct impact of their work.