Deep Merge JSON Configs | Dataford Interview Questions

Write a clean, reusable utility function to deep-merge two complex JSON configuration objects, handling edge cases like array merging and null values.

Implement deep_merge(base, override). Recursively merge dictionaries, concatenate lists in order, and use the override value for scalars, type conflicts, and explicit null values. Return a new JSON-compatible value without mutating either input.

Input values may contain only dictionaries, lists, strings, numbers, booleans, and None. The function must return the merged value.

Constraints

Inputs contain only JSON-compatible values: dictionaries, lists, strings, numbers, booleans, and null.
Dictionary keys are strings.
Nested structures may have arbitrary depth within the language recursion limit.
The function must not mutate either input.
When both values are lists, concatenate them in base-then-override order.

Function Signature

def deep_merge(base, override):

Your question is Deep Merge JSON Configs. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Write a clean, reusable utility function to deep-merge two complex JSON configuration objects, handling edge cases like array merging and null values.

Input values may contain only dictionaries, lists, strings, numbers, booleans, and None. The function must return the merged value.

Constraints

Inputs contain only JSON-compatible values: dictionaries, lists, strings, numbers, booleans, and null.
Dictionary keys are strings.
Nested structures may have arbitrary depth within the language recursion limit.
The function must not mutate either input.
When both values are lists, concatenate them in base-then-override order.

Function Signature

def deep_merge(base, override):

Your question is Deep Merge JSON Configs. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.