Chuẩn bị cho MongoDB Certified DBA (C100DBA) exam – Part I


Section 1: Philosophy & Features:

1. Which of the following does MongoDB use to provide High Availability and fault tolerance?
a. Write Concern
b. Replication
c. Sharding
d. Indexing
2. Which of the following does MongoDB use to provide High Scalability?
a. Write Concern
b. Replication
c. Sharding
d. Indexing

Section 2: CRUD Operations:

1. Which of the following is a valid insert statement in mongodb? Select all valid.
a. db.test.insert({x:2,y:”apple”})
b. db.test.push({x:2,y:”apple”})
c. db.test.insert({“x”:2, “y”:”apple”})
d. db.test.insert({x:2},{y:”apple”})

Section 3: Aggregation Framework:

1. Which of the following is true about aggregation framework?
a. A single aggregation framework operator can be used more than once in a query
b. Each aggregation operator need to return atleast one of more documents as a result
c. Pipeline expressions are stateless except accumulator expressions used with $group operator
d.  the aggregate command operates on a multiple collection

Section 4: Indexing:

Below is a sample document in a given collection test.
{ a : 5, b : 3, c: 2, d : 1 }
1. Given a compound index { a: 1, b:1, c:1, d:1}, Which of the below query will not use in-memory sorting? Select all valid.
a. db.test.find( { a: 5, b: 3 } ).sort( { a: 1, b: 1, c: 1 } )
b. db.test.find( { a: 5, b: 3 } ).sort( { a: 1} )
c. db.test.find( { a: 5, b: 3 } ).sort( {c: 1 } )
d. db.test.find( { a: 5, b: 3 } ).sort( { c: 1, d : 1 } )

Section 5: Replication:

1. In a replicated cluster, which of the following node would only be used during an election?
a. primary
b. secondary
c. arbiter
d. hidden
2. What  is the first task that a secondary would perform on being prompted by another secondary for an election?
a. Start the election process for primary
b. Connect to primary to confirm its availability
c. Vote for the first secondary so that it would become the next primary
d. Vote for itself and then call for election

Section 6: Sharding:

1. In which of the following scenarios is sharding not the correct option. Select all that apply.
a. The working set in the collection is expected to grow very large in size
b. The write operations on the collection are low
c. The collection is a read intensive collection with less working set
d. The write operations on the collection are very high

Section 7: Server & Application Administration:

1. Which of the following collections stores authentication credentials in MongoDB?
a. system.users
b. local.users
c. test.users
d. users.users

Section 8: Backup & Restore:

1. In a sharded cluster, from which node does one stop the balancer process before initiating backup?
a. Any node
b. mongos node
c. config server node
d. replicaset primary node

Answers


Section 1: Philosophy & Features:
1. b
2. c
Section 2: CRUD Operations
1. a,c
Section 3: Aggregation Framework
1. a,b,c
Section 4: Indexing
1. c,d
Section 5: Replication
1. c
2. b
Section:6 Sharding
1. b,c
Section 7: Server & Application Administration
1. a
Section 8: Backup & Restore
1. b

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