MONGODB · EASY CODEX

MongoDB Interview Questions — Easy

Q: What is MongoDB and how does it differ from traditional RDBMS?

Definition: MongoDB is a document-oriented NoSQL database that stores data in flexible, JSON-like documents (BSON format). Schema Difference: Traditional RDBMS uses a rigid schema with tables, rows, a

Q: What is BSON and how is it different from JSON?

Definition: BSON stands for Binary JSON. It is a binary-serialized representation of JSON-like documents. Size & Efficiency: BSON is designed for high speed and space efficiency. It is faster to parse

Q: Explain the structure of a MongoDB ObjectId.

Definition: A unique 12-byte identifier automatically generated as the primary key (id) for each document. Byte Breakdown: First 4 bytes: Unix timestamp (seconds since epoch) representing the creation

Q: What is a dynamic schema and what are its advantages?

Concept: MongoDB collections do not enforce document structure. Documents in the same collection can have different fields, types, and nested nesting. Advantages: Agility: Rapid development cycles sin

Q: What are collections and documents in MongoDB?

Collection: Equivalent to an RDBMS table. It is a grouping of MongoDB documents. Collections do not enforce schemas but can have schema validation rules if configured. Document: Equivalent to an RDBMS

Core concepts, definitions, basic syntax, and first principles expected in round 1 screening.

50 Theory Questions7 Implementation Folios5 Free Model Answers

THEORY QUESTIONS & SOLUTIONSShowing 5 of 50 questions

Q1What is MongoDB and how does it differ from traditional RDBMS?

Definition: MongoDB is a document-oriented NoSQL database that stores data in flexible, JSON-like documents (BSON format).
Schema Difference: Traditional RDBMS uses a rigid schema with tables, rows, and columns. MongoDB uses a schema-less structure with collections and documents, allowing varying structures within the same collection.
Relationships: RDBMS relies heavily on normalized tables and relations via foreign keys and joins. MongoDB relies on denormalized embedded documents or manual references, optimizing for read-heavy operations.
Scalability: RDBMS typically scales vertically (adding hardware power), while MongoDB scales horizontally (sharding across multiple servers).

Q2What is BSON and how is it different from JSON?

Definition: BSON stands for Binary JSON. It is a binary-serialized representation of JSON-like documents.
Size & Efficiency: BSON is designed for high speed and space efficiency. It is faster to parse and traverse compared to JSON.
Data Types: BSON extends JSON by supporting additional data types such as Date, ObjectId, BinData (binary data), Double, and 32-bit/64-bit integers. JSON only natively supports strings, numbers, booleans, null, arrays, and objects.

Q3Explain the structure of a MongoDB ObjectId.

Definition: A unique 12-byte identifier automatically generated as the primary key (_id) for each document.
Byte Breakdown:
- First 4 bytes: Unix timestamp (seconds since epoch) representing the creation time.
- Next 5 bytes: Random value unique to the machine and process (ensures uniqueness across distributed systems).
- Last 3 bytes: An incrementing counter, initialized with a random value.
Implication: ObjectIds are naturally ordered by creation time, allowing sorting by _id to act as a chronological sort.

Q4What is a dynamic schema and what are its advantages?

Concept: MongoDB collections do not enforce document structure. Documents in the same collection can have different fields, types, and nested nesting.
Advantages:
- Agility: Rapid development cycles since database migrations or schema alterations (ALTER TABLE) are not required.
- Polymorphism: Ability to represent diverse entities or semi-structured data without complex join tables.
- No Null Fields: Eliminates the need to store null values for optional attributes, saving storage space.

Q5What are collections and documents in MongoDB?

Collection: Equivalent to an RDBMS table. It is a grouping of MongoDB documents. Collections do not enforce schemas but can have schema validation rules if configured.
Document: Equivalent to an RDBMS row. It is the basic unit of data in MongoDB, composed of key-value pairs stored in BSON format.

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