Aggregations like count() & avg() can bring down your database as data grows. They're time bombs that can crater at any moment, making it hard to scale predictably. Use DynamoDB or avoid aggregations for a scalable system.

AppSync subscriptions can be complex due to their asynchronous nature & tied mutations. Learn how to test them effectively using Jest & AWS Amplify, choosing between "wide" (resource service) or "narrow" (event handler) testing approaches.

Serverless tech simplifies ownership & app running, abstracting away complexity like VPCs, making it easier for devs to focus on building value quickly.