MongoDB provides high availability with replica sets. A replica set consists of two or more copies of the data. Each replica set member may act in the role of primary or secondary replica at any time. All writes and reads are done on the primary replica by default. Secondary replicas maintain a copy of the data of the primary using built-in replication. When a primary replica fails, the replica set automatically conducts an election process to determine which secondary should become the primary. Secondaries can optionally serve read operations, but that data is only eventually consistent by default.
AngularJS is referred to as a client-side framework and is used in front-end web development with high efficiency and potentially to develop high-end web applications.AngularJS, a client-side framework. MongoDB stores data in a JSON-like format and AngularJS allows the client to seamlessly send and receive JSON documents.