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How To Screen and Hire a MongoDB Developer? With the right interview questions

Ihor Shcherbinin
VP of Recruiting at DistantJob - - - 3 min. to read

While SQL databases are very popular, NoSQL databases have their use cases as well. MongoDB, a type of NoSQL database, offers more flexibility and is very affordable. You need to hire a MongoDB developer if you have vast, unpredictable data.

Data is increasing exponentially each year, so trying to store, process, and analyze everything can seem impossible. A good MongoDB developer can help with this. But how do you find a good MongoDB developer? By screening it properly with the right interview questions.

What is MongoDB?

Document-based databases, with MongoDB being the most popular, group data more logically and don’t involve the Structured Query Language (hence the name NoSQL). MongoDB is the leading NoSQL database for a few different reasons, such as being open-source and cross-platform compatible.

MongoDB works by storing data in JSON-like documents in varying structures. If you hire a MongoDB developer, they should be able to explain that this database uses dynamic schemas, which means that it isn’t necessary to define the structure (including fields or types) before creating records.

Additionally, it’s simple to add or delete fields by changing the structure of records, called documents in Mongo. A MongoDB developer should be able to simply store complex data structures and take advantage of the high availability and scalability that MongoDB was built for.

If you hire a MongoDB developer, they should also be able to make use of its many built-in features to help you access your data quickly and flexibly. It’s the database component used in the MEAN software stack and is compatible with .NET applications, Java, and more.

Companies like The Weather Channel and Expedia have a team of talented MongoDB developers who utilize MongoDB to store huge volumes of data that aren’t particularly structured. MongoDB helps give data flexibility and high availability in a cloud environment. It quickly develops, updates, and releases new data structures, and efficiently scales database architecture.

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Why Hire a MongoDB Developer?

Beyond all of this, what makes MongoDB important?

1. A MongoDB Developer can Store Unstructured Data in Large Volumes

MongoDB allows users to save a lot of data with little or no structure. This is important for things like a customer’s location that continually changes or past purchases which consistently grow.

Once you hire a MongoDB developer, they will be able to add different types of data without setting limits on the database. It’s impossible to overstress how useful this flexibility is if it’s necessary for you.

2. Quick Development

Once again, this database’s flexibility comes in handy. If you hire a MongoDB developer who is talented, they can frequently add, update, or delete data structures without wasting much downtime between the numerous versions. On the other hand, trying to modify a relational database will undoubtedly go more slowly.

The dynamic schemas in MongoDB help your developer’s ability to attempt to incorporate or change anything within the database quickly.

3. A MongoDB Developer can Efficiently Scale Your Database Architecture

This database helps make it easy to spread data out, either across on-site servers or in the cloud, with their built-in sharding solutions. This also enables you to make the most of cloud computing.

Keyt MongoDB Developer Interview Questions of 2021

Now that you know why you need to hire a MongoDB developer, it’s time to find out what interview questions to ask them. Keep in mind that if you want to skip the tricky part of searching for a developer and interviewing them, we can quickly find you a well-vetted, guaranteed expert.

1. What is a Namespace?

This is a question that a good MongoDB developer can answer easily. In MongoDB, a Namespace is the database name and collection name concatenated. For example, company  employees has employees as a collection and the company as the database.

2. Does MongoDB Require Much RAM?

This question can help you understand if you are preparing to hire a MongoDB developer who fully understands this database. They should know that MongoDB can run on a small amount of RAM as it dynamically allocates and deallocates RAM depending on what is necessary.

3. What is the Structure of ObjectID in MongoDB?

If the MongoDB developer knows the subject well, they’ll be able to give this answer.

This returns a 12-byte ObjectId value that consists of:

  • A 4-byte value representing the seconds since the Unix epoch,
  • A 3-byte machine identifier
  • A 2-byte process id, and
  • A 3-byte counter, starting with a random value

4. Explain What Sharding is and Why it’s Useful

Sharding is “a method for distributing data across multiple machines.” It is used in MongoDB to support deployments with particularly large data sets and high throughput operations.

If you have a database system with large data sets or high throughput applications, these can put a strain on the capacity of a single server. Hire a MongoDB developer who knows a solution to this.

The two methods for addressing system growth are by vertical and horizontal scaling.

Additionally, a sharded cluster consists of shard, mongos, and config servers:

  • “Shard: Each shard contains a subset of the sharded data. Each shard can be deployed as a replica set.
  • Mongos: The mongos acts as a query router, providing an interface between client applications and the sharded clusters.
  • Config servers: Config servers store metadata and configuration settings for the cluster. As of MongoDB 3.4, config servers must be deployed as a replica set (CSRS).”

5. Is it Possible to Isolate Your Cursors From Intervening With the Write Operations? If so, How?

Yes. You use the snapshot() method on a cursor. This isolates the operation for a specific case by traversing the index on the _id field, guaranteeing that the query will only return each document once.

6. Explain Create Operations and Give an Example

Create or insert operations are similar to most other databases. They add a new document to a collection, and if the collection doesn’t currently exist, the insert operation will create it. You can either insert one or insert many documents into a collection via these methods:


Each insert operation in MongoDB targets a specific collection. Here’s an example:



name: “sue”,

age: 26,

status: “pending



7. Explain and Give an Example of the Update Operation

As their name implies, update operations modify existing documents in a collection. There are three different methods you can use to update documents:

  • db.collection.updateOne()
  • db.collection.updateMany()
  • db.collection.replaceOne()

Hire a MongoDB developer who can give an example of any of these. We’ve decided to show how to use updateMany():


{ age: { $lt: 18 } },

{ $set: { status: “reject” } }


Hire The Best Remote MongoDB Developer For Your Business with DistantJob

Now, you have all of the tools you need to understand why you’d like to hire a MongoDB developer as well as the interview questions to ask them. If you’d like to have a highly-vetted, guaranteed expert sent to you, just head to DistantJob hiring page and let us do all of the hard work for you.

Ihor Shcherbinin

Ihor, is the VP of Recruiting at DistantJob. He specializes in sourcing and placing top remote developers for North American companies. His expertise covers the entire recruiting cycle, from pinpointing job needs to finalizing hires. Known for his skill in remote staffing solutions and offshore team integration, Ihor excels in matching the best tech talents with U.S. organizations. His approach to virtual developer hiring is marked by insightful candidate selection and strategic offer negotiation, ensuring the right fit for every role.

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