I'm trying to get my hands dirty with GCP. One part I'm not sure about is, what happens if you use a service which is in the paid tier for example Kubernetes. The GCP site mentions the following
"We ask you for your credit card to make sure you are not a robot. You won’t be charged unless you manually upgrade to a paid account."
Does this mean, it stops me by default if I try to use something which is in the paid tier? even after I exceed the free credits and the free time period expires?
There are multiple levels with Google Cloud Billing.
The first is Free Tier. This level includes services that are free of charge provided you stay within the offering limits. link Provided you stay within those limits, your $300 initial credit is not used.
The next is Free Trial. This program provides you with $300 in credits to use within 90 days. You must provide a credit card to obtain these credits. Unless you also upgrade to a Paid Account, you cannot use services that require payment. This also means your credit card will not be charged with the exception of around a dollar to verify the card which is refunded. Once you use up your free credits you will either have to close your account or upgrade to paid.
The final level is Paid Account. This means you can use services that are outside the scope of the other two offerings. However, this does not mean you can use each and every service. New accounts will have quotas established that limit some/all services. You can request quota increases (similar to a credit line increase request). You can continue to use your $300 credit even with a Paid Account. You do not lose your credit by upgrading.
My recommendation is to stay at the Free Trial level, learn more about Google Cloud services while also investing some time to learn about the pricing structure for various services. Your credit card is protected, meaning no unexpected charges. Once you feel comfortable with Google Cloud, upgrade to Paid Account.