The database layer, which is also known as the data tier, stores all the information related to user profiles and transactions. Essentially, it contains any data that needs to persist in being stored in the data tier. This information is sent back to the application layer for logic processing and then, eventually, it renders to the user in the web layer. For example, if the user is logged in to a website with their user ID and password, then the application layer verifies the user credentials with information stored in the database. If the credentials match the stored information, the user is allowed to log in and access the authorized area of the website.
The architect may choose to build a data tier in relational databases, for example, PostgreSQL, MariaDB, Oracle Database, MySQL, Microsoft SQL Server, Amazon Aurora, or Amazon RDS. The architect may also add a NoSQL database such as Amazon DynamoDB, MongoDB, or Apache Cassandra. The data tier is not only used to store...
