To help Etsy sellers support charitable causes with every purchase in their shops, I developed a sevice that integrated with Etsy's API. This service made it easy for sellers to support one or more causes and promote those causes as part of their marketing plans. With the promotion tools, sellers could choose suggested messaging or provide their own, and the messaging would be pushed to selected listings in their shops, even placing a banner on the listings' primary images if desired.
I developed the base website design with Materialize, and I built most new sections of the site from static mockups that a coworker designed, matching the mockups exactly in many cases.
I made heavy use of queued jobs with Amazon SQS to support horizontal scaling across worker nodes. I used Elastic Beanstalk for easy load balancing and deployment of the main application, as well as ElastiCache with Redis for the caching layer. RDS with MySQL served as the database backend. I built most of the UI with React.js, making AJAX calls to load resources as needed.