It is a Platform as a Service (PaaS) offering
Allows to quickly deploy and scale web-applications without having to manage the underlying infrastructure

Features

Supports multiple programming languages (Node.js, Java, Python, PHP, [[c-sharp|C#]])
Allows user to bring own language runtime (achieved using custom containers)

Provides robust monitoring and diagnostics:

  • Cloud Monitoring and Cloud Logging
  • Cloud Debugger and Error Reporting

Application Versioning
Allows to create different environments (staging, production, development)

Traffic Splitting
Route incoming traffic to different app versions, A/B test and incremental feature rollout

Application Security
Define access rules with App Engine Firewall, uses SSL/TLS certificates by default

Environments

App Engine has two types of environments: Flexible and Standard
Both can be simultaneously used by the application
App Engine is well suited for applications designed using the microservice architecture

Standard EnvironmentFlexible Environment
Serverless ComputeFully Managed Containers
Starts in SecondsStarts in Minutes
Runs in Sandboxed EnvironmentRuns with Docker Containers on Compute Engine (VMs)
Designed for rapid scaling (sudden traffic spikes)Designed for predicable and consistent traffic
Supports specific language versions, not custom runtimeSupports any language version and custom runtime
Can scale to zero instancesMust have at least one instance running
Pricing based on hours usedPricing based on vCPUs, Memory and Disk
Cannot use SSH to debugCan use SSH to debug
No background processesCan have background processes