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Discord·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Jun 2026Remote

Summary

A one-hour technical round for a Data Engineer role at Discord that was basically a Python data design exercise. Nothing crazy algorithmic, but the problem had enough moving parts that I kept second-guessing my structure halfway through.

Questions Asked (5)

Q1

Design a dictionary structure to represent a game's information (name, genre, country, release date) and its associated Discord servers, where game data should be sourced from something like Wikipedia.

Data ModelingSystem Design
Author's notes

This felt more open-ended than I expected.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scope, then propose a normalized data model with separate entities for games and Discord servers, linked by a foreign key. Discuss data sourcing from Wikipedia, including API integration, caching, and data freshness, and explain how the model supports Discord's use cases like server discovery.

Pro tip: Emphasize data integrity and scalability: use a unique game identifier (e.g., Wikipedia page ID) as the primary key to avoid duplicates, and consider denormalizing frequently accessed fields for read-heavy workloads.

1. Clarify Requirements

Ask about expected scale, read/write patterns, and whether real-time updates are needed. Confirm if Discord servers are user-generated or official.

2. Design Core Entities

Define a Game entity with fields: id, name, genre, country, release_date, and a source_url. Define a DiscordServer entity with fields: id, name, invite_link, member_count, and game_id as a foreign key.

3. Integrate Wikipedia Data

Outline a pipeline to fetch game data from Wikipedia's API, parse infoboxes, and store it. Include caching and periodic refresh to handle updates.

4. Address Scalability and Access Patterns

Discuss indexing on game_id and genre for fast lookups, and consider denormalizing game name into the server entity if reads are frequent. Mention sharding or replication if needed.

5. Handle Edge Cases and Data Quality

Cover duplicate games, missing fields, and conflicting data. Propose validation rules and fallback mechanisms, such as manual curation or multiple sources.

Key Points to Mention

  • Normalization vs. denormalization trade-offs for read-heavy Discord use cases
  • Using Wikipedia's API (e.g., MediaWiki) and handling rate limits
  • Caching strategies (e.g., Redis) to reduce latency and API calls
  • Data freshness: scheduled jobs vs. event-driven updates
  • Indexing and query optimization for server discovery by game
  • Data integrity: unique constraints, foreign keys, and conflict resolution

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

Q2

Given a list of game dictionaries, implement a function get_genre(input_game) that returns the genre for a given game name.

Algorithms & Data Structures
Author's notes

Straightforward lookup.

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AI HintsAI Generated

Suggested Approach

Clarify the input format and constraints, then propose a solution that balances simplicity and efficiency. Start with a straightforward linear search, but discuss optimizations like building a hash map for O(1) lookups if the function is called frequently. Consider edge cases such as missing games or duplicate names.

Pro tip: Demonstrate awareness of real-world usage: at Discord, this function might be called millions of times, so precomputing a dictionary mapping game names to genres is often the best approach. Also, mention that you'd handle case sensitivity and whitespace to ensure robustness.

1. Clarify requirements and constraints

Ask about the size of the list, frequency of calls, and whether the list can change. Confirm the expected behavior for missing games (e.g., return None or raise an error).

2. Choose the right data structure

If the function is called once, a linear scan is fine. If called repeatedly, build a hash map (dictionary) from game name to genre for O(1) lookups.

3. Implement the function

Write clean code that handles edge cases: normalize input (e.g., lowercase, strip), check for missing keys, and return the genre or appropriate default.

4. Analyze time and space complexity

Explain the trade-offs: linear search is O(n) time and O(1) space; hash map is O(n) preprocessing and O(1) lookup, using O(n) space.

5. Test and discuss extensions

Walk through test cases (existing game, missing game, duplicate names). Mention potential extensions like caching or handling multiple genres.

Key Points to Mention

  • Time and space complexity trade-offs between linear search and hash map
  • Handling edge cases: missing game, duplicate names, case sensitivity
  • Input validation and normalization (e.g., stripping whitespace, lowercasing)
  • Scalability considerations for frequent calls (precomputing a lookup table)
  • Choice of return value for missing games (None, default string, or exception)
  • Potential for caching or memoization if the list is static

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

Q3

Implement get_games(input_genre) that returns all games belonging to a given genre.

Algorithms & Data Structures
Author's notes

Easy filter.

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AI HintsAI Generated

Suggested Approach

Clarify the data model and constraints first, then propose an efficient solution using a hash map from genre to list of games for O(1) lookup. Discuss trade-offs between preprocessing and on-the-fly filtering, and consider edge cases like multiple genres per game or missing genres.

Pro tip: Mention that if the dataset is static, you can preprocess an index once to make repeated queries fast; if dynamic, consider maintaining the index incrementally. This shows you think about real-world usage at Discord where game data may change.

1. Clarify requirements and data model

Ask about the structure of game objects, whether a game can have multiple genres, the expected size of the dataset, and how often the function will be called. This ensures you design the right solution.

2. Choose data structures

Decide between a simple linear scan (O(n) per query) and a precomputed hash map (O(1) per query after O(n) preprocessing). Consider memory vs. speed trade-offs.

3. Outline the algorithm

If using a hash map, iterate through all games once, and for each genre the game belongs to, append the game to the corresponding list. Handle multiple genres per game by adding to each relevant list.

4. Handle edge cases

Discuss what to return for an unknown genre (empty list), games with no genre, or null inputs. Also consider case sensitivity and genre aliases.

5. Analyze complexity and trade-offs

State time and space complexity for both approaches. Explain when to use each based on query frequency and dataset mutability.

Key Points to Mention

  • Time complexity: O(n) preprocessing + O(1) per query vs. O(n) per query for linear scan.
  • Space complexity: O(n) for the hash map index.
  • Handling games with multiple genres by adding to multiple lists.
  • Edge cases: unknown genre returns empty list, null/empty inputs.
  • Immutability and thread-safety if the index is shared across requests.
  • Potential for caching or lazy initialization if the dataset is large.

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

Q4

Implement get_most_available_games(games) that returns the game or games with the highest number of platforms.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

This one tripped me up slightly because I forgot to account for ties at first.

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AI HintsAI Generated

Suggested Approach

Clarify the input structure and expected output format, then propose a single-pass solution that tracks the maximum platform count and collects all games achieving it. Discuss time and space complexity, and consider edge cases like empty input or ties.

Pro tip: Mention that returning multiple games in case of ties is a key requirement, and that a single pass avoids unnecessary sorting or multiple iterations, which is efficient for large datasets.

1. Clarify requirements

Confirm the data structure of each game (e.g., dictionary with 'platforms' list) and that the output should be a list of games with the highest platform count, including all ties.

2. Design algorithm

Use a single pass: initialize max_count and result list. For each game, compute platform count; if greater than max_count, update max_count and reset result; if equal, append to result.

3. Analyze complexity

State that time complexity is O(n) where n is number of games, and space complexity is O(k) where k is number of games with max platforms (for the result list).

4. Handle edge cases

Discuss empty input (return empty list), games with no platforms, and ties. Ensure the solution works for any iterable of games.

5. Implement and test

Write clean code with meaningful variable names, and walk through a small example to verify correctness, including a tie scenario.

Key Points to Mention

  • Single-pass O(n) time complexity
  • Handling ties by collecting all games with max platform count
  • Edge cases: empty input, games with zero platforms
  • Space complexity O(k) for result list
  • Avoiding unnecessary sorting or multiple passes
  • Clarifying input/output format before coding

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

Q5

Implement get_available_games(number_of_platform) that returns all games available on exactly that number of platforms.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

Another filter, basically the same shape as get_games.

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AI HintsAI Generated

Suggested Approach

First, clarify the input data structure and the definition of 'available on exactly that number of platforms.' Then, propose an efficient algorithm, such as building a mapping from game to platform count and filtering, while discussing trade-offs between time and space complexity. Finally, walk through the implementation and test with edge cases.

Pro tip: Demonstrate awareness of real-world data by asking whether platform availability is static or dynamic, and whether the function should handle large datasets or be called frequently. This shows you think about scalability and maintainability, which is crucial at Discord.

1. Clarify requirements and assumptions

Ask about the input format (e.g., list of games with platform lists, or a mapping) and confirm that 'exactly that number' means the count of distinct platforms. Also clarify if the result should be sorted or if duplicates matter.

2. Choose data structures and algorithm

Decide on an approach: iterate through games, count platforms per game, and collect those matching the target count. Consider using a hash map for O(1) lookups if needed, or simply filter with a list comprehension.

3. Analyze complexity and trade-offs

Discuss time and space complexity: O(N*P) where N is number of games and P is average platforms per game, or O(N) if platform counts are precomputed. Mention if precomputation is worth it for repeated calls.

4. Implement and test

Write clean code with meaningful variable names. Test with edge cases: no games match, all games match, empty input, and games with zero platforms.

5. Consider extensions and optimizations

If the function is called frequently with different counts, suggest precomputing a mapping from platform count to list of games. Also discuss handling dynamic updates if data changes.

Key Points to Mention

  • Time and space complexity analysis (e.g., O(N*P) vs O(N) with precomputation)
  • Choice of data structures: hash map for counting, list for results
  • Edge cases: empty input, no matches, games with zero platforms
  • Trade-offs between one-time filtering and precomputing for repeated calls
  • Clarifying questions about input format and definition of 'available'
  • Scalability considerations for large datasets or frequent calls

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