Salesforce·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Salesforce SWE interview with a JSON flattening problem. Pretty much a pure coding round, one question, no system design or behavioral stuff from what I could tell. The problem itself was interesting but the edge cases are where things get tricky.

Questions Asked (1)

Given a nested JSON object (with arbitrary depth, containing objects and arrays), flatten it into a single-level key-value mapping and serialize it to a string. Keys should represent the full path using dot notation for object fields and bracket notation for array indices.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I started with recursion and it worked fine for the basic cases.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements and edge cases, then outline a recursive depth-first traversal that builds the path as it descends. For each leaf value, append the path and value to the result, then serialize the flat map to a string (e.g., JSON).

Pro tip: Mention that you would use an explicit stack or recursion with a path array to avoid string concatenation overhead, and discuss how to handle special characters in keys (e.g., escaping dots or brackets) to ensure unambiguous paths.

1. Clarify requirements and edge cases

Ask about the expected output format (e.g., JSON string), handling of null values, empty objects/arrays, and special characters in keys. Confirm the notation for arrays (e.g., [0]) and objects (e.g., .key).

2. Choose traversal strategy

Decide between recursive DFS or iterative stack-based traversal. Discuss trade-offs: recursion is simpler but may risk stack overflow for very deep structures; iterative avoids that but is more complex.

3. Build the flattened map

Traverse the structure, maintaining the current path. For objects, append '.key'; for arrays, append '[index]'. When a leaf (non-object/array) is reached, add the path-value pair to the result map.

4. Serialize to string

Convert the flat map to a string, typically using JSON.stringify. Ensure the output is a valid single-level JSON object with string keys and values.

5. Test and validate

Walk through examples, including nested arrays and objects, and verify the output. Discuss potential pitfalls like circular references (if applicable) and how to handle them.

Key Points to Mention

Recursive vs iterative traversal and their trade-offs (stack depth, readability).
Path construction using dot notation for objects and bracket notation for arrays.
Handling of edge cases: empty objects/arrays, null values, special characters in keys.
Serialization method: JSON.stringify or custom serializer, and ensuring valid output.
Time and space complexity: O(n) time where n is total number of nodes, O(d) space for recursion depth.
Potential need for escaping or quoting keys that contain dots or brackets to avoid ambiguity.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.