MongoDB has a free tier with a decent powerful cluster that you can experiment with.
The good news is that the Free Tier is free for eternity and you don’t have to add any credit card.
New to Atlas?
If you are new to Atlas, MongoDB Atlas is a fully managed global cloud database with automation and proven practices. It guarantees scalability, availability and compliance. It is available on 70+ regions across GCP, AQWS and Azure. Of course, the most popular ones are also available in the free tier.
You are not limited if you first start with a free tier. Because if you decide you want something more powerful, upgrading to a larger tier is very easy. To get yourself an account, sign up for Atlas today.