Which format/standard is used by MongoDB internally to store documents?

Question

Options

• AJSON
• BBSON
• CB+ Trees
• DJSON - Extended

• A
  92% (24)
• C
  4% (1)
• D
  4% (1)

Explanation

There's an error in the question as provided: the marked "Correct Answer: A (JSON)" is wrong. The actual correct answer is B. BSON.

MongoDB internally stores documents in BSON (Binary JSON), a binary-encoded serialization format that extends JSON with additional data types like Date, ObjectId, int32/int64, and BinData. While MongoDB accepts JSON-like syntax from clients, it converts and stores data as BSON because binary encoding enables faster parsing, richer type support, and efficient traversal.

Why the distractors are wrong:

• A. JSON - JSON is the human-readable text format you query MongoDB with at the application layer, but it is not what MongoDB stores internally; BSON is.
• C. B+ Trees - B+ Trees are an index data structure (used by databases like MySQL/PostgreSQL), not a document storage format.
• D. JSON - Extended - "Extended JSON" (ejson) is a MongoDB specification for representing BSON types in JSON text, used for tools like mongoexport, but it is not the internal storage format.

Memory tip: Think BSON = Binary JSON - the "B" stands for both Binary and MongoDB's internal Backing store. If a question asks what's "under the hood" in MongoDB, the answer is always BSON.

Note for whoever created this question: Please correct the answer key - option B is correct, not A.

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