Here are some examples of sequence diagrams you can create in Eraser:

Web App [icon: layout] > DB [icon: database]: Start transaction
Web App > Cloud Fx [icon: function]: Call function
Cloud Fx > API [icon: cloud-cog]: Create session
API > Cloud Fx: Session info
Cloud Fx > DB: Create tx record
Cloud Fx > API: Request access token
API > Cloud Fx: Access token
Cloud Fx > Web App: Token and transaction info
Web App > API: Complete transaction
alt [label: If successful]{
  API > Web App: Transaction confirmation
else [label: If failed]{
  API > Web App: Transaction cancellation
Web App > DB: Create tx record
Web App > API: Subscribe to transaction changes
activate API 
API > API: Ongoing events
API > Web App: Push events
deactivate API

Open in Eraser to duplicate.