MassLight builds startups in exchange for equity. Most of our engineers are full-stack but some of our engineers prefer frontend or backend. https://masslight.com
We're currently building zapEHR https://zapehr.com, a backend for building healthcare applications.
You can check out and apply to one of our job postings on AngelList https://angel.co/company/masslight/jobs, and if you have any questions email me at jsaewitz@masslight.com.