Using sync for new images implies that you will continue to use your onprem and keep synchronizing it forever, Sync just once for the old images, new images go directly to google cloud via pub/sub, and eventually get rid of the onprem.

Cloud SQL supports SQL Server, Since the IT team ' s attention is being focused on other activities, they will have less time for existing admin tasks, It would be best to take a managed/hosted version.

https://cloud.google.com/blog/products/devops-sre/sre-fundamentals-slis-slas-and-slos

Apigee includes analytics services which allow enterprises to report on various aspects of an API.

Firebase Cloud Messaging:

Firebase Cloud Messaging (FCM) is a cross-platform messaging solution that lets you reliably send messages at no cost.

Using FCM, you can notify a client app that new email or other data is available to sync. You can send notification messages to drive user re-engagement and retention. For use cases such as instant messaging, a message can transfer a payload of up to 4000 bytes to a client app.

Key capabilities of Firebase Cloud Messaging:

Send notification messages or data messages:  Send notification messages that are displayed to your user. Or send data messages and determine completely what happens in your application code.

Versatile message targeting:  Distribute messages to your client app in any of 3 ways—to single devices, to groups of devices, or to devices subscribed to topics.

Send messages from client apps:  Send acknowledgments, chats, and other messages from devices back to your server over FCM’s reliable and battery-efficient connection channel.

Community Cloud  – The cloud infrastructure is planned for selective use by a particular community of consumers from organizations that have mutual interests like security needs, policy, and compliance considerations.

Reference link -  https://csrc.nist.gov/glossary/term/community_cloud

Cloud Armor provides DDoS protection for applications. It can also " Filter your incoming traffic based on IPv4 and IPv6 addresses or CIDRs. Enforce geography-based access controls to allow or deny traffic based on source geo using Google’s geoIP mapping. "

Cloud Datastore is the best for semi-structured application data that is used in app engines ' applications. Bigtable is best for analytical data with heavy read/write events like AdTech, Financial or IoT data. Cloud Storage is best for structured and unstructured, binary or object data like images, large media files and backups. SQL is best for web frameworks and in existing applications like storing user credentials and customer orders. Cloud Spanner is best for large scale database applications that are larger than two terabytes; for example, for financial trading and e-commerce use cases. As I mentioned at the beginning of the module, depending on your application, you might use one or several of these services to get the job done.

What is Infrastructure as a service :

IaaS (infrastructure as a service) is a computing model that offers resources on-demand to businesses and individuals via the cloud.

IaaS is attractive because acquiring computing resources to run applications or store data the traditional way requires time and capital. Enterprises must purchase equipment through procurement processes that can take months. They must invest in physical spaces: typically specialized rooms with power and cooling. And after deploying the systems, enterprises need IT, professionals, to manage them.

All this is challenging to scale when demand spikes or the business grows. Enterprises risk running out of capacity or overbuilding and ending up with infrastructure that suffers from low utilization.

These challenges are why IaaS use is steadily growing. Learn more about Compute Engine, Cloud Storage, etc.

Multi-region option will use multiple datacenters that are within the European Union. More regions will also help with lower latency since users are spread across the European U.

https://cloud.google.com/storage/docs/locations#considerations