MongoDB certification
I recently managed to get certified with the C100DEV: MongoDB Certified Developer Associate Exam and C100DBA: MongoDB Certified Developer DBA Associate Exam. In this article I want to share my experience and say what you should pay attention to when preparing, and how the exam passed. I will also give some examples of questions.
University.mongodb.com project site
Cost
Each exam costs $ 150.00. Each retake is paid . But there is a system of discounts. If I'm sorry public traning, then a promotional code is given for a 50% discount. I could not find information about this on the site until after the end of the training course the promotional code itself came to my mail.
The threshold for passing the exam
To pass, you need to score 490 points out of 600. If you take into account that there are only 600 questions, and I scored 525 points, then most likely points are also counted for partially correct answers.
Passing exam
Examination sessions are held for 2 weeks with breaks of 1-2 months. That is, at any time you can’t pass the exam. The exam is an online test. To take the exam, the GoToMeeting program is installed. In it, through a video chat, you contact the company representative (I constantly came across Indians with a strange accent of the English language). He dictates to you the general rules (about the rules below). Next, you configure access to your PC. He enters the password on the site to access the exam.
Rules for passing the exam (I will list only the most basic ones):
- you need to be in the room alone, no one should enter (it is better to warn loved ones if you are at home so that no one comes in)
- no phone numbers
- do not talk to anyone (keep quiet throughout the exam)
- you cannot turn off webcams
- you cannot look around
- you cannot use third-party programs (the console to test the request, documentation)
- you can use google translate
Throughout the exam, you sit in front of the webcam with expanded access to your PC and the examiner observes you. Once I thought, looked away and immediately received a comment from the inspector, I had to turn the webcam to the side to show that there was nothing there. By the way, before the exam through the webcam we show that there is a clean table, no one is in the room. They even asked me to show what's under the table.
results
Results are available 3 weeks after the exam. The score is sent to the mail with the details of the sections. For example CRUD 85%, aggregation 90%, indexing 75%, sharding: 50%. According to the results of the exams, you fall into the MongoDB Certified Professional Finder database (analogue of yellow pages zend certification)
Preparation
For preparation, I used docs.mongodb.org I just took and re-read all the sections. It turned out to be very helpful. You can also take any free public training (https://university.mongodb.com/training). There were questions from the exam. From the fact that I did not like it - it's boring videos where there is a lot of water.
Sample Questions
For the C100DEV exam, the following sections:
-Philosophy & Features (General Concept)
- CRUD (working with data)
- Indexing
- Aggregation
- Data Modeling
- Replication
- Sharding
I will give some examples of questions from the exam:
The index {a: 1, b: 1 is built on the collection}
What queries will use it:
- db.data.find ({a: {$ gt: 4}}) .sort ({a: 1, b: 1})
- db.data.find ({a: 5, b: {$ lt: 3}}) .sort ( {b: 1})
- db.data.find ({b: 5}) .sort ({a: 1})
- db.data.find ({a: 1})
- db.data.find ({b : 2})
Which of the following will return a query db.records.find ({a: {$ exists: true}})
- {_id: 0, a: 1}
- {_id: 1, a: {b: 1} }
- {_id: 2, a: [1,2,4]}
- {_id: 3, a: null}
- {_id: 4}
Which of the following is true about the capped collection
- you can’t change the size
— documents are stored sorted on the hard disk
— you cannot move documents
— you cannot change the size of documents (do an update with an increase in the size of the document)
- you cannot delete documents
— you cannot rename
Dan composite index {a: 1, b: 1, c: 1, d: 1}. Which queries will not use in-memory sorting
- db.test.find ({a: 5, b: 3}) .sort ({a: 1, b: 1, c: 1})
- db.test.find ( {a: 5, b: 3}) .sort ({a: 1})
- db.test.find ({a: 5, b: 3}) .sort ({c: 1})
- db.test. find ({a: 5, b: 3}) .sort ({c: 1, d: 1}) The
collection contains the following data:
{a: [5]},
{a: [5,3]},
{a: [3]},
{a: [3, 'dsfasf']}
How to get only one document {a: [5,3] }
- find ({a: [5,3]})
- find ({a: {$ and: [3,5]}})
- find ({a: {$ all: [3,5]}})
What is stored in the first 4 bytes of ObjectId?
- identifier of the machine on which ObjectId
is generated - identifier of the process
- time timestamp
How many maximum nodes are allowed in the replica set
- 27
- 50
- 100
It is necessary to look at the operation of the operators $ all, $ addToset, $ pull, $ push, $ slice, $ in, $ text
How to create a user, index creation syntax, get a list of indexes. What are mongofiles, mongosniff, mongotop, mongostat, bsondump, mongorestore, mongodump used for. Where does explain () work. How many maximum voting nodes are in a replica set. What is an arbiter. The syntax of basic operations (insert, distinct, remove, update etc.)
Given the configuration for sharding and questions like: on which nodes the request will be executed.
For example, sharding is organized by {a: 1, b: 1}
Which queries make it possible to unambiguously determine which balls the query will work on (instead of chasing all at once)
a> 1
a = 1 and b> 2
b> a
For exam C100DBA more questions on administration and ready to tell in a separate article.
University.mongodb.com project site
Cost
Each exam costs $ 150.00. Each retake is paid . But there is a system of discounts. If I'm sorry public traning, then a promotional code is given for a 50% discount. I could not find information about this on the site until after the end of the training course the promotional code itself came to my mail.
The threshold for passing the exam
To pass, you need to score 490 points out of 600. If you take into account that there are only 600 questions, and I scored 525 points, then most likely points are also counted for partially correct answers.
Passing exam
Examination sessions are held for 2 weeks with breaks of 1-2 months. That is, at any time you can’t pass the exam. The exam is an online test. To take the exam, the GoToMeeting program is installed. In it, through a video chat, you contact the company representative (I constantly came across Indians with a strange accent of the English language). He dictates to you the general rules (about the rules below). Next, you configure access to your PC. He enters the password on the site to access the exam.
Rules for passing the exam (I will list only the most basic ones):
- you need to be in the room alone, no one should enter (it is better to warn loved ones if you are at home so that no one comes in)
- no phone numbers
- do not talk to anyone (keep quiet throughout the exam)
- you cannot turn off webcams
- you cannot look around
- you cannot use third-party programs (the console to test the request, documentation)
- you can use google translate
Throughout the exam, you sit in front of the webcam with expanded access to your PC and the examiner observes you. Once I thought, looked away and immediately received a comment from the inspector, I had to turn the webcam to the side to show that there was nothing there. By the way, before the exam through the webcam we show that there is a clean table, no one is in the room. They even asked me to show what's under the table.
results
Results are available 3 weeks after the exam. The score is sent to the mail with the details of the sections. For example CRUD 85%, aggregation 90%, indexing 75%, sharding: 50%. According to the results of the exams, you fall into the MongoDB Certified Professional Finder database (analogue of yellow pages zend certification)
Preparation
For preparation, I used docs.mongodb.org I just took and re-read all the sections. It turned out to be very helpful. You can also take any free public training (https://university.mongodb.com/training). There were questions from the exam. From the fact that I did not like it - it's boring videos where there is a lot of water.
Sample Questions
For the C100DEV exam, the following sections:
-Philosophy & Features (General Concept)
- CRUD (working with data)
- Indexing
- Aggregation
- Data Modeling
- Replication
- Sharding
I will give some examples of questions from the exam:
The index {a: 1, b: 1 is built on the collection}
What queries will use it:
- db.data.find ({a: {$ gt: 4}}) .sort ({a: 1, b: 1})
- db.data.find ({a: 5, b: {$ lt: 3}}) .sort ( {b: 1})
- db.data.find ({b: 5}) .sort ({a: 1})
- db.data.find ({a: 1})
- db.data.find ({b : 2})
Which of the following will return a query db.records.find ({a: {$ exists: true}})
- {_id: 0, a: 1}
- {_id: 1, a: {b: 1} }
- {_id: 2, a: [1,2,4]}
- {_id: 3, a: null}
- {_id: 4}
Which of the following is true about the capped collection
- you can’t change the size
— documents are stored sorted on the hard disk
— you cannot move documents
— you cannot change the size of documents (do an update with an increase in the size of the document)
- you cannot delete documents
— you cannot rename
Dan composite index {a: 1, b: 1, c: 1, d: 1}. Which queries will not use in-memory sorting
- db.test.find ({a: 5, b: 3}) .sort ({a: 1, b: 1, c: 1})
- db.test.find ( {a: 5, b: 3}) .sort ({a: 1})
- db.test.find ({a: 5, b: 3}) .sort ({c: 1})
- db.test. find ({a: 5, b: 3}) .sort ({c: 1, d: 1}) The
collection contains the following data:
{a: [5]},
{a: [5,3]},
{a: [3]},
{a: [3, 'dsfasf']}
How to get only one document {a: [5,3] }
- find ({a: [5,3]})
- find ({a: {$ and: [3,5]}})
- find ({a: {$ all: [3,5]}})
What is stored in the first 4 bytes of ObjectId?
- identifier of the machine on which ObjectId
is generated - identifier of the process
- time timestamp
How many maximum nodes are allowed in the replica set
- 27
- 50
- 100
It is necessary to look at the operation of the operators $ all, $ addToset, $ pull, $ push, $ slice, $ in, $ text
How to create a user, index creation syntax, get a list of indexes. What are mongofiles, mongosniff, mongotop, mongostat, bsondump, mongorestore, mongodump used for. Where does explain () work. How many maximum voting nodes are in a replica set. What is an arbiter. The syntax of basic operations (insert, distinct, remove, update etc.)
Given the configuration for sharding and questions like: on which nodes the request will be executed.
For example, sharding is organized by {a: 1, b: 1}
Which queries make it possible to unambiguously determine which balls the query will work on (instead of chasing all at once)
a> 1
a = 1 and b> 2
b> a
For exam C100DBA more questions on administration and ready to tell in a separate article.