Salesforce·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Salesforce coding screen with one meaty recursive problem. The question itself was straightforward to describe but had enough edge cases to keep you busy for the whole session.

Questions Asked (1)

Given a potentially nested JSON object (string keys mapping to either values or more nested objects), write a function that flattens it into a single-level string where nested keys are joined by dots. For example, {"a": {"b": 1}, "c": 2} becomes "a.b=1, c=2". Implement it recursively, and be ready to discuss how you'd handle values that are lists.

Algorithms & Data StructuresTechnical Trade-offsAPI & Integrations

Author's notes

Started fine, got the recursive case working pretty quickly.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem: confirm the output format, how to handle lists, and edge cases like empty objects or null values. Then outline a recursive solution that builds a path of keys and accumulates flattened key-value pairs. Finally, discuss trade-offs and extensions, such as iterative approaches or handling lists by either indexing or serializing them.

Pro tip: Mention that you'd use a helper function with a prefix parameter to avoid string concatenation overhead, and that you'd consider using an array to collect results and join at the end for efficiency. Also, proactively ask about the expected behavior for lists (e.g., index-based flattening vs. JSON stringification) to show you think about edge cases.

1. Clarify requirements and edge cases

Ask about the exact output format, how to handle lists, null values, empty objects, and whether keys can contain dots. Confirm if the output should be a string or a data structure.

2. Design recursive approach

Explain that you'll traverse the object recursively, maintaining a path of keys. For each key-value pair, if the value is an object, recurse with the extended path; otherwise, add the flattened key-value to the result.

3. Implement with helper function

Write a helper function that takes the current object, a prefix string, and an accumulator (e.g., array of strings). Use a loop over keys, build the new prefix, and recurse or append as needed.

4. Handle lists explicitly

Discuss options: treat lists as leaf values (e.g., JSON.stringify), or flatten with indices (e.g., 'a.0.b=1'). Mention that the choice depends on requirements and that you'd confirm with the interviewer.

5. Analyze complexity and trade-offs

State time complexity O(n) where n is total number of nodes, and space O(d) for recursion depth. Mention iterative alternative using a stack to avoid recursion limits, and trade-offs between readability and performance.

Key Points to Mention

Recursive traversal with a path parameter to build dot-separated keys.
Handling of non-object values (primitives, arrays, null) as leaves.
Edge cases: empty objects, nested empty objects, keys with dots, and null values.
Time and space complexity: O(n) time, O(d) space for recursion depth.
Alternative iterative approach using a stack to avoid recursion depth limits.
Output formatting: joining key-value pairs with commas and spaces as per example.

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