Notice: Over the next few months, we're reorganizing the App Engine documentation site to make it easier to find content and better align with the rest of Google Cloud products. The same content will be available, but the navigation will now match the rest of the Cloud products. If you have feedback or questions as you navigate the site, click Send Feedback Stay organized with collections Save and categorize content based on your preferences App Engine offers you a choice between two environments for Java applications: standard environment and flexible environment. Both environments have the same code-centric developer workflow, scale quickly and efficiently to handle increasing demand, and enable you to use GoogleâÃÂÃÂs proven serving technology to build your web, mobile, and IoT applications quickly and with minimal operational overhead. While the available environments have a lot in common, they differ in a few important ways Choose your preferred environment Standard environment Optimized to scale nearly instantaneously to handle huge traffic spikes Most cost-effective for applications that have significant periods where they are not serving traffic OpenJDK based Java runtime supports the standard public Java library Doesn't impose a security manager--your code won't be restricted by Java permissions issues.