The On-Call Holiday Notifier is a Ruby AWS Lambda function I built from scratch to prevent a simple but costly problem: on-call engineers getting paged during their paid time off, or worse, nobody realizing the on-call schedule had a gap during a holiday.
The function runs on a schedule and cross-references three data sources:
PagerDuty for the current on-call roster, BambooHR for employee PTO and
location data, and iCalendar feeds for region-specific company holidays (Envato
has offices across multiple countries). When a conflict is detected — an
on-caller scheduled during their PTO or a regional holiday — it sends a
structured alert to the #customer-on-call Slack channel so the team can
arrange coverage.
I built the entire project: gem scaffolding, all API integrations (PagerDuty, BambooHR, Slack, iCalendar parsing), the Lambda handler, comprehensive test coverage with Timecop for time-dependent behavior, and the Buildkite CI pipeline. A similar concept to SOS Bot at A2 Hosting years later — small automation that prevents real operational gaps.