I have been working with AWS (Amazon Web Services) for a couple of years now, and decided to attain the Solutions Architect Associate exam. You can take a look here at an overview of the content. AWS certifications must be re-taken every 3 years, as they are constantly evolving.
AWS is without question the biggest of all the cloud service providers (Google, Microsoft, Oracle) and it has massive scale with multipleavailability zones and regions across all the biggest continents.
If you have no experience in AWS, no excuses - you can sign up for the AWS Free Tier here and get 12 months free access to all of the cloud services. It is an excellent way to learn it hands-on if you are not lucky enough to be working in an AWS environment. 
$ AWS
Solutions Architect Associate Certification (redacted)
Exam Overview
$ AWS
Global Regions
# AWS Services I would recommend learning
S3
Amazon Simple Storage Service (Amazon S3) is an object storage service offering
industry-leading scalability, data availability, security, and performance.
EC2
Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides secure,
resizable compute capacity in the cloud.
VPC
Amazon Virtual Private Cloud (Amazon VPC) gives you full control over your virtual
networking environment, including resource placement, connectivity, and security.
Route 53
Amazon Route 53 is a highly available and scalable cloud Domain Name System (DNS)
web service.
Transit Gateway
AWS Transit Gateway connects VPCs and on-premises networks through a central hub.
This simplifies your network and puts an end to complex peering relationships.
It acts as a cloud router – each new connection is only made once.