This serverless solution sends Trello card reminders directly to WhatsApp using AWS Lambda, Step Functions, and EventBridge. When a due date is set or updated, Trello webhooks trigger an AWS workflow that schedules and delivers timely notifications.

The setup integrates API Gateway, DynamoDB Streams, and Meta's WhatsApp API to manage state and deliver messages. A filtering Step Function ensures only relevant Trello events (like due date changes) are processed, minimizing unnecessary compute.

Developers can self-host this automation for under $1/month, avoiding commercial integration costs. Key components include secure credential storage via AWS Parameter Store and dynamic WhatsApp message templates approved through Meta's review process.