Free Preparation Discussions
MENU
MongoDB C100DBA Exam Questions
- Topic 1: Philosophy and Features: This topic of the C100DBA exam, assesses MongoDB Database Administrators on their understanding of MongoDB's core characteristics, its differences from RDBMS databases, access and administration methods, and the concept of sharding. Mastery here ensures a strong foundational knowledge of MongoDB philosophy.
- Topic 2: CRUD: This topic of the MongoDB Certified DBA Associate exam evaluates administrators on creating, reading, updating, and deleting documents. It measures the ability to handle structured document insertion, updates, upserts, deletions, and query operations. Proficiency in CRUD operations is vital for daily MongoDB database management.
- Topic 3: Indexes: The C100DBA exam tests knowledge of aspiring MongoDB Database Administrators on optimizing query performance through indexing. Administrators must identify appropriate indexes, understand explain plan outputs, and resolve index-related errors. Effective indexing skills enhance MongoDB database efficiency and performance.
- Topic 4: Server Administration: This topic of the MongoDB Certified DBA Associate exam focuses on essential server management tasks. MongoDB Database Administrators must demonstrate proficiency in starting, stopping, and configuring mongod, using mongosh, and managing replica sets. Competence in server administration is crucial for maintaining MongoDB database operations.
- Topic 5: Monitoring: This topic examines the ability to monitor database performance and health. MongoDB Database Administrators should identify alerts, use currentOp, monitor active operations, and manage storage effectively. Strong monitoring skills ensure the MongoDB database runs smoothly and efficiently.
- Topic 6: Security: The topic assesses the ability to secure MongoDB environments. MongoDB Database Administrators attempting the C100DBA exam must understand TLS, authentication, role-based authorization, encryption, and audit logging. Robust security skills protect MongoDB data integrity and ensure compliance with security standards.
- Topic 7: Replication: It evaluates understanding of replication processes. MongoDB Database Administrators should grasp the roles of primary and secondary nodes, read preferences, rs.status, write concern, and elections. Effective replication management ensures high availability and data redundancy.
- Topic 8: Backup and Recovery: This topic of the C100DBA exam, tests the ability to create backups of replica sets. MongoDB Database Administrators need to know backup procedures to safeguard data and ensure recovery in case of failures. Proficiency here is critical for maintaining data continuity and integrity.
Free MongoDB C100DBA Exam Actual Questions
Note: Premium Questions for C100DBA were last updated On Oct. 30, 2026 (see below)
What command set removes node-1.cluster1.mycompany.local:27017 and node-2.cluster1.mycompany.local:27017 from the replica set, then adds node-1.cluster1.mycompany.local:27017 back to the replica set?
The supported mongosh helpers for replica-set membership changes are rs.remove() and rs.add(). rs.remove(hostname) removes the member whose host string matches the supplied host:port, while rs.add() adds a new member using either a host string or a member configuration document that includes a host field. Option C uses those documented methods in the required sequence: remove node 1, remove node 2, then add node 1 back. The names rs.removeNode() and rs.addNode() shown in the other options are not standard MongoDB replica-set helper methods. Membership changes must be performed carefully because modifying voting or data-bearing membership can affect majority calculations, elections, and availability. Administrators normally execute membership changes while connected to the current primary, allow configuration propagation, and verify replica-set health afterward with rs.status() or related diagnostics. If a removed data-bearing node is later re-added, it may need to synchronize depending on how far its data has diverged from the current replica-set history. Among the choices, option C is the only valid command sequence.
Study Guide reference/topic:Cluster Reliability and Data Resilience - replica-set membership, rs.remove(), rs.add(), and topology changes.
===========
What command lists all indexes for a collection?
db.collection.getIndexes() is the mongosh method used to return the definitions of all indexes that currently exist on a collection. The result is an array of index specification documents that can show fields such as the index name, key pattern, index version, uniqueness, partial-filter settings, sparse configuration, collation, and whether the index is hidden. This makes the method useful for index audits, troubleshooting, and confirming the physical indexes available to the query planner. Option A is not a documented method for enumerating collection indexes. Option B resembles the $indexStats aggregation stage, which reports usage statistics for indexes, but db.collection.indexStats() is not the method used to list full index definitions. Option C, findIndexes(), is also not the documented mongosh collection helper. Administrators should distinguish between listing index definitions, examining index usage, and inspecting an individual query's winning plan: getIndexes() addresses the first requirement, $indexStats addresses usage metrics, and explain() addresses query-planner behavior. Therefore option D is the correct command for listing all indexes on the collection.
Study Guide reference/topic:Indexing and Query Optimization - index administration, index metadata, and db.collection.getIndexes().
===========
You are comparing values of different BSON types in mongodb. You want to compare from lowest to highest. Which comparison order is used?
A department store maintains a clothing collection:
{ "_id": 1, "item": "sweater", "sizes": [ "XS", "S", "L" ] }
{ "_id": 2, "item": "t-shirt", "sizes": [ "S", "M", "L" ] }
{ "_id": 3, "item": "vest", "sizes": [ "M", "L", "XL", "XXL" ] }
An employee runs:
db.clothing.find( { "sizes": "M" } )
Which index should improve performance for this query the MOST?
The query filters only on the sizes field, so the most direct supporting index is a single-field index on sizes. Because sizes contains arrays, MongoDB automatically treats the resulting index as a multikey index and creates index entries derived from the array elements. That allows the query { sizes: 'M' } to locate matching documents through the index rather than scanning every document in the collection. Option B indexes item, which is not part of the predicate and therefore does not help this query. Option C contains sizes, but _id is the leading key and the query provides no equality restriction on _id; this prevents efficient use of the later key as a standalone prefix for the query. Option D has the same structural problem because item precedes sizes and is not constrained. MongoDB's index-prefix rules make a targeted { sizes: 1 } index the strongest choice here. In a real workload, DBAs should also consider write overhead and whether additional queries can share a compound index before creating redundant indexes. For this single query pattern, option A is optimal.
Study Guide reference/topic:Indexing and Query Optimization - multikey indexes, array fields, index prefixes, and query support.
===========
- Select Question Types you want
- Set your Desired Pass Percentage
- Allocate Time (Hours : Minutes)
- Create Multiple Practice tests with Limited Questions
- Customer Support
Olivia Miller
1 month agoPaul Green
2 months agoAdam Cook
3 months agoEmily Martin
4 months agoApplication Administration White
5 months agoEmma Hill
5 months agoReplication White
6 months agoSharding Smith
5 months agoCRUD Wilson
3 months agoServer Administration Clark
2 months agoBetty Johnson
6 months agoThomas King
6 months agoJames Baker
6 months agoMonica Phillips
6 months agoMaria Howard
6 months agoDonald Rodriguez
6 months agoJonelle
7 months agoMelina
7 months agoSuzan
7 months agoNichelle
8 months agoJerry
8 months agoThaddeus
8 months agoChantay
8 months agoMicah
9 months agoTrevor
9 months agoReiko
9 months agoAlyce
9 months agoJames
10 months agoAnabel
10 months agoAntione
10 months agoMicaela
10 months agoFrance
11 months agoKris
11 months agoHelene
11 months agoFrederick
11 months agoMargart
12 months agoDorthy
12 months agoKaitlyn
1 year agoNana
1 year agoSherita
1 year agoGilma
1 year agoLouvenia
1 year agoJulianna
1 year agoWerner
1 year agoJamal
1 year agoLemuel
1 year agoArt
1 year agoGlennis
1 year agoSimona
1 year agoDorthy
1 year agoFernanda
1 year agoAndree
1 year agoMa
2 years agoLaura
2 years agoNieves
2 years agoMona
2 years agoTawanna
2 years agoBernadine
2 years agoJaney
2 years agoBernardine
2 years agoDomonique
2 years agoLorita
2 years agoVernell
2 years agoNoemi
2 years agoAlison
2 years agoNickole
2 years agoLaura
2 years agoYasuko
2 years agoThurman
2 years agoZana
2 years agoNickolas
2 years agoLatrice
2 years agoTerrilyn
2 years agoDesirae
2 years agoJeffrey
2 years agoGianna
2 years agoMatthew
2 years agoFreeman
2 years agoToi
2 years agoIesha
2 years agoJesusita
2 years agoAntonio
2 years agoShalon
2 years agoTwanna
2 years agoJenifer
2 years agoEsteban
2 years agoFrederick
2 years ago