MongoDB is a serverless, distributed database orientated towards documents, in other words, saving data in BSON documents instead of registries, making it much more expressive and powerful. It's got all the advantages and usages of a relational database, but being more flexible and dynamic.

The MondoDB Atlas is a database on a global cloud created with modern applications in mind, and it's distributed and safe by default, alongside being managed in AWS, Google Cloud and Azure.

Amazon Aurora Serverless is an on-demand, auto-scaling configuration for Amazon Aurora. It automatically starts up, shuts down, and scales capacity up or down based on your application's needs. It enables you to run your database in the cloud without managing any database capacity.

With Aurora Serverless, you simply create a database endpoint, optionally specify the desired database capacity range, and connect your applications. You pay on a per-second basis for the database capacity you use when the database is active, and migrate between standard and serverless configurations with a few clicks in the Amazon RDS Management Console.

Plans

• Shared: Free forever with a M0 cluster, with a 512MB storage capacity, and shared RAM. Also has M2 and M5 versions available with a monthly fee of $9 and $25 respectively. Great for learning and exploring about MongoDB.
  
• Serverless: For serverless applications with a variable traffic that's generally on the lower values. It requires a minimal amount of configuration. Has a free of $0.30 per read, and has extra frees according to the operations you do.
• Dedicated: For production applications that have a sophisticated workload requirement, has advanced configuration controls, with cluster prices ranging from $0.08 to to $33.26/hr.

Example Pricing

Applications with 10M reads ($2.75), 1M writes ($1.25), 1GB storage ($0.25) and 1GB data transfer ($0.015-0.10 according to traffic): $4.3 USD tops.

A wide variety of payment methods exist, with the smallest database starting at an upfront $243, or $24.82 monthly for a year.

Onboarding

Great documentation to start off quickly, with a free plan that's very quick to access. Has a wide amount of resources and guides to learn about it.

Scalability

Automatic, and scalable both horizontally (sharding) and vertically.

Regions​

MongoDB Atlas supports  the following regions: Americas, Asia Pacific, Europe, Middle East and Africa. The choice of cloud provider and region affects network latency for clients accessing your database deployment and the cost of running the database deployment. For clusters, this choice also affects the configuration options for the available cluster tiers. The region refers to the physical location of your MongoDB database deployment.

Backup

​MongoDB Atlas, the official MongoDB cloud service, provides 2 fully-managed methods for backups:

• ​Continuous Backups, which take incremental backups of data in your cluster, ensuring your backups are typically just a few seconds behind the operational system. Atlas continuous backups allow you to restore from stored snapshots or from a selected point in time within the last 24 hours. You can also query a continuous backup snapshot.
• Cloud Provider Snapshots, which provide localized backup storage using the native snapshot functionality of the cluster's cloud service provider.

Security

​MongoDB provides various features, such as authentication, access control, encryption, to secure your MongoDB deployments. Some key security features include: Authentication, SCRAM, Role-Based Access Control, Transport Encryption, among others.

Onboarding
Good documentation that includes tutorials.

Scalability
On-demand auto scaling configuration, sharding.

Regions
US, Africa, Asia Pacific, China, South America, Middle East and Europe. The support varies across specific versions of each database engine, and across AWS Regions.

 
Backups 
Aurora backs up your cluster volume automatically and retains restore data for the length of the backup retention period. You can specify a backup retention period, from 1 to 35 days, when you create or modify a DB cluster.  Aurora backups are stored in Amazon S3.

Security
By default, Aurora Serverless v1 uses the Transport Layer Security/Secure Sockets Layer (TLS/SSL) protocol to encrypt communications between clients and your Aurora Serverless v1 DB cluster. It supports TLS/SSL versions 1.0, 1.1, and 1.2.

MongoDB is a document database with the scalability and flexibility that you want with the querying and indexing that you need. MongoDB’s document model is simple for developers to learn and use, while still providing all the capabilities needed to meet the most complex requirements at any scale. 

• Rich on JSON Documents
• Allows arrays and nested items as values
• Rich and expressive consulting language
• Filter and order on any field, regardless of the way it's inserted in the document
• Full ACID transactions
• Allows for combinations on inquiries
• Completely automatized
• Security Copy
• Global Clusters

• Compatible with MySQL and PostgreSQL
  
• High-performance storage subsystem
  
• Automates and standardizes database clustering and replication
• Supports the full breadth of Aurora features, including Global Database, Multi-AZ deployments, and read replicas.
  
• Takes advantage of the familiar Amazon Relational Database Service (Amazon RDS) features for management and administration.