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LinkedIn·Data Scientist·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

LinkedIn Data Scientist interview with a SQL-heavy analytical task. The problem was structured in two parts and centered on a job activity table, escalating from basic aggregation to a tricky filtering edge case that I didn't fully see coming.

Questions Asked (2)

Q1

Given a job activity table with job_id, candidate_id, and activity_type (either 'view' or 'apply'), calculate for each job: total activities, unique candidates who viewed, and unique candidates who applied.

Product Analytics & MetricsData Modeling
Author's notes

Pretty standard aggregation stuff.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the table schema and the grain of the data, then outline a SQL query that groups by job_id and uses conditional aggregation with COUNT(DISTINCT CASE WHEN ...) to compute the three metrics. Explain how you would handle edge cases like duplicate activities and ensure the query is efficient for large datasets.

Pro tip: Mention that you would validate the results by checking that unique viewers and appliers are subsets of total activities, and consider whether the funnel metrics should be computed at the job level or also segmented by time or candidate attributes.

1. Clarify requirements and data model

Confirm the table structure, the meaning of each column, and whether activities can be duplicated. Ask if the metrics should be calculated over all time or a specific period.

2. Outline the aggregation logic

Explain that you will group by job_id and use conditional aggregation to count distinct candidates for views and applies separately, while total activities is a simple count of all rows.

3. Write the SQL query

Construct a query using COUNT(*) for total activities and COUNT(DISTINCT CASE WHEN activity_type = 'view' THEN candidate_id END) for unique viewers, similarly for appliers.

4. Address edge cases and performance

Discuss handling NULLs, duplicate rows, and large data volumes. Mention indexing on job_id and activity_type, and possibly using approximate distinct counts if scale is huge.

5. Validate and interpret results

Suggest sanity checks like ensuring unique viewers and appliers are less than or equal to total activities, and explain how these metrics inform product decisions.

Key Points to Mention

  • Use of COUNT(DISTINCT) with CASE statements for conditional aggregation
  • Importance of grouping by job_id to get per-job metrics
  • Handling of duplicate activities (e.g., a candidate viewing multiple times)
  • Consideration of time windows or segmentation for deeper insights
  • Performance implications and potential need for indexing or approximate counts
  • Business interpretation: view-to-apply conversion rate and funnel analysis

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

Q2

Recalculate those same metrics but exclude any candidate who applied without ever having viewed any job. How do you handle someone who applies to multiple jobs but has zero views across all of them?

Product Analytics & MetricsRoot Cause AnalysisData Modeling
Author's notes

This is where I fumbled a bit.

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AI HintsAI Generated

Suggested Approach

First, clarify the metric definitions and the business context for excluding zero-view applicants, then walk through the SQL/Pandas logic to recalculate, and finally propose a principled treatment for multi-job applicants with zero views—likely a separate segment or exclusion with clear documentation. Emphasize that the decision should align with the metric's purpose (e.g., measuring engagement vs. conversion).

Pro tip: Proactively mention that zero-view applicants might represent a distinct user segment (e.g., auto-apply or bot traffic) and suggest analyzing their behavior separately before deciding to exclude them, showing you think beyond the immediate ask.

1. Clarify definitions and purpose

Confirm what 'viewed any job' means (e.g., job detail page view) and why we're excluding zero-view applicants—likely to focus on engaged users. Ask if the goal is to measure conversion or engagement.

2. Recalculate metrics with exclusion

Write pseudocode/SQL to filter out applicants with zero views across all jobs, then recompute the metrics (e.g., apply rate, view-to-apply ratio). Show before/after comparison.

3. Handle multi-job zero-view applicants

Decide whether to exclude them entirely or treat as a separate segment. If excluded, note the impact on sample size and potential bias; if kept, analyze their behavior separately.

4. Validate and interpret results

Check for data quality issues (e.g., logging errors) and assess if the exclusion changes conclusions. Discuss implications for product decisions.

Key Points to Mention

  • Define 'view' precisely (e.g., job detail page view vs. impression) and ensure consistency.
  • Use SQL window functions or group-by to identify applicants with zero views across all jobs.
  • Consider that zero-view applicants may be bots, auto-apply users, or low-intent—segment them for analysis.
  • Document the exclusion criteria and its impact on metrics to maintain transparency.
  • Compare metrics before and after exclusion to understand the effect on key performance indicators.
  • Recommend a data-driven decision on whether to exclude or flag zero-view applicants based on their behavior.

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