Free MongoDB C100DBA Practice Exam with Questions & Answers

A replica-set secondary maintains a replicated copy of the primary ' s dataset. The primary records data-changing operations in its oplog, and secondary members continuously copy and apply those oplog entries asynchronously to keep their data synchronized. This redundancy allows an eligible secondary to participate in an election and potentially become primary if the current primary becomes unavailable. mongos, option B, is the query-routing process used in a sharded cluster; it does not store an application dataset copy. An arbiter, option C, participates in replica-set voting and elections but deliberately does not maintain a copy of the database data. A shard, option D, is a data partition in a sharded cluster and is normally implemented as a replica set in production, but “shard” is not the replica-set member role that replicates the primary ' s data. Secondary behavior is central to MongoDB high availability, read-scaling options, backup strategies, and failover. Administrators monitor secondary replication lag and health to ensure the copies remain sufficiently current. Therefore the member responsible for maintaining copies of the primary ' s data is the secondary, making option A correct.

Study Guide reference/topic:Cluster Reliability and Data Resilience - replica-set primaries, secondaries, oplog replication, and redundancy.

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mongosh accepts a MongoDB host address in hostname:port form, so mongosh " node-1.cluster1.mycompany.local:27017 " is the valid choice among the commands shown. A canonical URI form such as mongosh " mongodb://node-1.cluster1.mycompany.local:27017 " is also valid, and the connection can alternatively be expressed using --host together with --port. Option A uses an unsupported --hostname switch rather than the documented --host option. Option B invents a --connect flag that is not the standard mongosh interface. Option C constructs an invalid string using an ampersand-style parameter rather than a MongoDB URI or a normal host:port target. Port 27017 is MongoDB ' s default server port, so it could often be omitted if the deployment uses the default, but explicitly including it is valid and removes ambiguity. In authenticated or TLS-enabled environments, the DBA would also supply credentials, authentication database, certificate settings, or a connection string carrying those parameters. For the simple host-and-port requirement in the question, option D is correct.

Study Guide reference/topic:Security, Networking, and Encryption - mongosh connectivity, host/port addressing, and connection options.

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Queryable Encryption is designed for client-side protection of sensitive fields while preserving supported query capabilities over encrypted values. With this model, appropriately configured client drivers encrypt selected fields before data is transmitted to the MongoDB server and decrypt authorized results on the client side. That architecture is well suited to highly sensitive PII such as government identification numbers, dates of birth, or regulated demographic information because the database server stores encrypted field values rather than plaintext for those protected fields. The Encrypted Storage Engine, option A, protects database files at rest but the server can still process decrypted data internally. TLS/SSL, option B, protects data while it is moving across the network, not the application field values from the database server itself. Role-Based Access Control, option C, restricts which authenticated principals can perform actions but does not itself cryptographically protect the field contents. Queryable Encryption complements, rather than replaces, TLS, authentication, authorization, auditing, and storage encryption. For the specific requirement of client-side encryption of sensitive application data, option D is the correct MongoDB feature.

Study Guide reference/topic:Security, Networking, and Encryption - Queryable Encryption, client-side encryption, sensitive fields, and key management.

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