Questions

1 of 19

1How to Connect to MongoDB server from Node.js application?

2How to create/ insert a record in MongoDB via Node.js?

3How to read records in MongoDB via Node.js?

4What is Query Selectors/Query Operators?

5What is Projection Operators?

6How can we modify documents?

7How do we update arrays in the MongoDB documents?

8How do we Insert or Update in a Single Operation?

9How do we delete documents in a collection?

10How would you handle a 'Bulk Write' failure mid-way through 10,000 documents?

11Explain the impact of an 'Upsert' on a high-write collection with multiple indexes.

12How does MongoDB handle Write Concern (w: 1 vs w: majority) and what are the latency trade-offs?

13What is a 'Covered Query' and how do you design one using Projection?

14How does the WiredTiger engine handle concurrency during a massive updateMany operation?

15What is the difference between replaceOne and updateOne with $set in terms of performance and BSON size?

16How do you update an element inside a deeply nested array using Array Filters (arrayFilters)?

17What are the operational risks of running a deleteMany({}) on a collection with millions of records?

18Is data truly removed from the disk immediately after a delete?

19You are scraping 1 million products per day using Puppeteer. If a product price changes, you need to update it, but if it's new, you must insert it. You also need to track the 'Last Seen' timestamp. How would you structure this CRUD operation to be most efficient?

MongoDB

Bulk Operations

01 / 19

How to Connect to MongoDB server from Node.js application?

MongoDB can be connected from Node by calling the connect() method of MongoClient class.

javascript

Difficulty: 4/10

Topics: connection string, authentication, connection pooling

Scenario Questions

0-2 years experience

1
We have a simple Node.js script that needs to read a collection from a local MongoDB. How would you establish the connection?
2
If you forget to include the database name in the connection string, what will happen when you run a query?
3
During startup the app crashes with a connection error. What steps do you take to handle that gracefully?

2-5 years experience

1
Your new feature writes logs to MongoDB, but after deployment you see intermittent MongoNetworkError timeouts. How would you debug and resolve this?
2
You need to support separate dev and prod MongoDB credentials without hard‑coding them. How would you structure the connection code?
3
Explain why you might enable the unified topology option and what impact it has on connection handling.

5-8 years experience

1
At high load the service opens many connections and memory usage spikes. How would you redesign the connection handling to be more efficient?
2
Describe how you would implement a graceful shutdown that ensures all pending MongoDB operations finish before the process exits.
3
What configuration would you choose for connection pooling and retry logic for a microservice handling thousands of requests per second?

8+ years experience

1
Our monolith is being split into multiple services, each needing MongoDB access. What architectural pattern would you use for managing connections across services?
2
How would you design a shared MongoDB connection library that satisfies security, observability, and versioning requirements across several teams?
3
If we need multi‑region read/write with eventual consistency, how does that affect your connection strategy and driver options?

Follow-up Questions

❓Can you sketch the minimal code you would write?
❓What would you monitor to know the connection is healthy?
❓How would you test connection failures in CI?