HubSpot Marketplace App Developer

Project Overview We have an existing, working API (already built and in use — several clients have manually integrated it into their own HubSpot portals). We want to package this API as a native app that can be listed on the HubSpot App Marketplace, so that any HubSpot user can install it directly and get instant results from our API without any custom development on their end. This is not a HubSpot CMS, theme, or landing page project. We need someone who has specifically built and shipped apps on HubSpot's Developer Platform for the App Marketplace — not just internal CRM customization. We have a rough idea of how this could work (e.g. an app card on a CRM record, a custom workflow action, etc.) but we're not locked into a specific approach. Part of what we're hiring for is your recommendation on the best way to structure this given our use case — we want someone who can advise on architecture, not just execute a fixed spec. What We Need Built A HubSpot Marketplace app that wraps our existing API and returns results to the end user inside HubSpot Your recommendation on the right HubSpot surface for this (app card / UI extension, custom workflow action, or another approach) based on what will actually work best for end users and get through Marketplace review cleanly A self-contained input form/flow that does NOT depend on the installing portal already having matching custom properties, since every customer's portal is configured differently A secure way to call our existing API (serverless function or equivalent) and handle the response A way to log/write results back to the relevant HubSpot record where applicable Public app install flow (OAuth) so any HubSpot portal can add it without our involvement Build on the current Developer Platform / Projects framework — not a legacy pattern, since HubSpot is sunsetting legacy CRM cards later this year Guidance and hands-on help getting the app through HubSpot's App Marketplace listing/certification review Ideal Candidate Has Shipped at least one app that is live and installable on the HubSpot App Marketplace (not just internal/private CRM cards) Hands-on experience with HubSpot's Developer Platform (UI Extensions, custom workflow actions, serverless functions) and can speak to the tradeoffs between approaches Experience with HubSpot's OAuth/public app install flow Comfortable integrating a third-party REST API into a HubSpot app Has been through HubSpot's app review/certification process before and can speak to what slows it down Not a Fit If Your HubSpot experience is primarily CMS Hub (HubL, themes, modules, landing pages) without Developer Platform app experience You've only built internal/private CRM cards for a single portal and haven't gone through Marketplace listing How We'll Work Together I'll be acting as project lead/product owner on this — I have the API and the business context. I'm looking for someone (or a small team) who can own the technical build end-to-end, advise on the right architecture, and walk me through key decisions, not someone who needs the spec fully pre-built. Regular check-ins, async updates welcome. To Apply, Please Include A link to a HubSpot Marketplace app you've built or contributed to (live listing preferred) A short note on your experience with HubSpot's app review/certification process Your initial thoughts on the best HubSpot surface for a use case like this, given the API already exists