How users see the services
Base and CoachBot are both served as web-apps with email notifications.
We don't currently offer "native" apps in the App Store, Google Play Store etc., since all of the services' features can be served via the web.
The web-apps are compatible with all modern browsers, and most regularly-used features are supported on mobile as well as desktop. With CoachBot, the team sessions are designed and scaled to work best on large screens: TVs or projectors.
The technology stack
Several other AWS services are used in support of this, like SageMaker for machine learning inference, SNS/SQS for job queues, API Gateway for endpoint protection.
Transactional emails (notifications, invites, reminders) are handled by Mailchimp/Mandrill.
Users' work calendars can be connected to CoachBot (as a means of login and to help schedule team/1:1 meetings). We use Cronofy to facilitate this connection, and support Google G Suite and Microsoft Office 365 calendars.
As we develop code, we peer-review major changes and feature additions, and use continuous integration to development infrastructure in a separate VPC. Releases to production happen with a pull request review with automated testing and database migrations.