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Early-stage Startup·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Coding round for a software engineer role, two parts to the same problem. The LRU cache piece was manageable but the compression follow-up caught me off guard and I fumbled the output format for a bit.

Questions Asked (2)

Q1

Implement an LRU cache structure that includes a snapshot function to print the current state of the cache.

Algorithms & Data StructuresSystem Design
Author's notes

Felt okay about this part.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements: cache capacity, operations (get, put, snapshot), and expected time complexity. Then design using a hash map and doubly linked list for O(1) operations, and implement snapshot by iterating over the list to print key-value pairs in order. Discuss trade-offs and potential optimizations.

Pro tip: In an early-stage startup, emphasize simplicity and extensibility: a clean, well-tested implementation with clear separation of concerns is often more valued than a highly optimized but complex solution. Also, consider how snapshot might be used for debugging or monitoring in production.

1. Clarify Requirements

Ask about cache capacity, expected operations, and snapshot format. Confirm if snapshot should be thread-safe or if it's for debugging only.

2. Choose Data Structures

Use a hash map for O(1) access and a doubly linked list to maintain recency order. Explain why this combination supports LRU eviction efficiently.

3. Implement Core Operations

Code get(key) and put(key, value) with O(1) time, updating the linked list and evicting the least recently used item when capacity is exceeded.

4. Implement Snapshot

Iterate through the linked list from most to least recently used, printing each key-value pair. Discuss time complexity O(n) and potential concurrency issues.

5. Test and Discuss Trade-offs

Walk through edge cases (empty cache, capacity 1, repeated keys) and mention alternative implementations (e.g., using OrderedDict in Python) and their trade-offs.

Key Points to Mention

  • O(1) time complexity for get and put using hash map + doubly linked list
  • LRU eviction policy: remove least recently used item when capacity is reached
  • Snapshot operation: iterate through linked list to print current state in order of recency
  • Thread safety considerations if snapshot is called concurrently with modifications
  • Edge cases: empty cache, single item, updating existing key, capacity zero
  • Alternative implementations (e.g., OrderedDict) and their trade-offs in simplicity vs control

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

Q2

Given a compression utility, compress the snapshot output so that entries with the same value are grouped together. For example, A:2 and B:2 would become 2 [A, B].

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

Did not see this coming.

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AI HintsAI Generated

Suggested Approach

First, clarify the input format and constraints (e.g., snapshot as list of key-value pairs, value types, memory limits). Then propose an efficient algorithm: build a hash map from value to list of keys, then output each group. Discuss trade-offs between time and space, and consider edge cases like duplicate keys or large datasets.

Pro tip: Mention that you would use a hash map for O(n) time complexity, but also consider if the output order matters and whether you can do it in-place to save memory. Showing awareness of practical constraints like memory limits or streaming data will impress early-stage startup interviewers.

1. Clarify requirements and constraints

Ask about input format (e.g., list of key-value pairs, dictionary), value types (comparable? hashable?), output format, and any constraints like memory or streaming.

2. Design the algorithm

Propose using a hash map to group keys by value: iterate through entries, append key to list for that value. Then output each value with its list of keys.

3. Analyze complexity and trade-offs

State time complexity O(n) and space O(n). Discuss alternatives (e.g., sorting if values are comparable) and when they might be better.

4. Handle edge cases

Consider empty input, duplicate keys, non-hashable values, and large datasets that don't fit in memory. Mention possible streaming or external sort approaches.

5. Write pseudocode or code

If asked, write clean pseudocode or code in a language of choice, explaining each step. Test with the given example.

Key Points to Mention

  • Hash map for O(n) grouping
  • Time and space complexity analysis
  • Edge cases: empty input, duplicate keys, non-hashable values
  • Trade-offs: sorting vs hashing, in-place vs extra space
  • Output format: value followed by list of keys
  • Scalability: handling large data with streaming or external sort

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