Google App Engine (GAE) is a platform as a service (PaaS) provided by Google. It allows developers to build and deploy web applications on Google's infrastructure. With GAE, developers can focus on writing code without worrying about the underlying infrastructure, scalability, and performance.

GAE supports multiple programming languages including Java, Python, C#, Node.js, and Go. It provides automatic scaling and load balancing, so applications can handle traffic spikes and high demand without manual intervention.

Some key features of Google App Engine include:

1. Scalability: GAE automatically scales applications to handle varying levels of traffic. It can scale both horizontally and vertically based on the workload.

2. High Availability: Applications deployed on GAE are hosted on a distributed infrastructure, ensuring high availability and resilience. Google's global network of data centers ensures that applications are accessible from anywhere.

3. Data Storage: GAE provides built-in storage options like Google Cloud Datastore and Google Cloud Storage. These allow developers to store and retrieve data in a scalable and reliable manner.

4. Integration with Other Google Services: GAE seamlessly integrates with other Google Cloud services such as Google Cloud BigQuery, Google Cloud Pub/Sub, and Google Cloud Machine Learning Engine, allowing developers to leverage additional functionalities.

5. Monitoring and Logging: GAE provides comprehensive monitoring and logging capabilities, allowing developers to track the performance and health of their applications.

6. Deployment and Versioning: GAE simplifies the deployment process, letting developers quickly deploy new versions of their applications. It also supports versioning, making it easy to roll back to a previous version if needed.

Overall, Google App Engine offers a scalable, managed platform for building and deploying web applications, freeing developers from infrastructure management and allowing them to focus on their code.