Compared: App Engine Standard & Flexible Environments

Comparison of  App Engine Standard & Flexible environments from the Google Cloud documentation -

Feature	Flexible environment	Standard environment
Instance startup time	Minutes	Seconds
Maximum request timeout	60 minutes	60 seconds
Background threads	Yes	Yes, with restrictions
Background processes	Yes	No
SSH debugging	Yes	No
Scaling	Manual, Automatic	Manual, Basic, Automatic
Scale to zero	No, minimum 1 instance	Yes
Writing to local disk	Yes, ephemeral (disk initialized on each VM startup)	No
Modifying the runtime	Yes (through Dockerfile)	No
Automatic in-place security patches	Yes (excludes container image runtime)	Yes
Network access	Yes	Node.js, Python 3, PHP 7.2, Go 1.11: Yes. Python, Go, and PHP (billing-enabled): Only via App Engine services (includes outbound sockets).
Supports installing third-party binaries	Yes	No
Location	North America, Asia Pacific, or Europe	North America, Asia Pacific, or Europe
Pricing	Based on usage of vCPU, memory, and persistent disks	Based on instance hours
Environment	Application instances run within Docker containers on Compute Engine virtual machines (VM).	Application instances run in a sandbox, using the runtime environment of a supported language listed below.
Optimal usage	Applications with the following characteristics: * Source code that is written in a version of any of the supported programming languages: Python, Java, Node.js, Go, Ruby, PHP, or .NET * Runs in a Docker container that includes a custom runtime or source code written in other programming languages. * Depends on other software, including operating system packages such as imagemagick, ffmpeg, libgit2, or others through apt-get. * Uses or depends on frameworks that include native code. * Accesses the resources or services of your Cloud Platform project that reside in the Compute Engine network. * Applications that receive consistent traffic, experience regular traffic fluctuations, or meet the parameters for scaling up and down gradually.	Applications with the following characteristics: * Source code is written in specific versions of the supported programming languages: Python 2.7, Python 3.7 (beta) Java 8, Java 7 Node.js 8 (beta) PHP 5.5, PHP 7.2 (beta) Go 1.6, 1.8, 1.9, and Go 1.11 (beta) * Intended to run for free or at very low cost, where you pay only for what you need and when you need it. For example, your application can scale to 0 instances when there is no traffic. * Applications that need to deal with rapid scaling...which experiences sudden and extreme spikes of traffic which require immediate scaling.