Dataford
Interview QuestionsInterview GuidesExperiencesCoaching
New
Pricing
Get started
Dataford
Popular roles
Software EngineerData AnalystData ScientistData EngineerBusiness AnalystAI EngineerMachine Learning EngineerProduct Manager
Browse
Browse All RolesEvery role hub, from analyst to MLBrowse All CompaniesCompany-specific interview loopsAll Interview GuidesThe full guide library
Top questions by role
Software EngineerData AnalystData ScientistData EngineerBusiness AnalystAI EngineerMachine Learning EngineerProduct Manager
Top questions by skill
SQLPythonStatisticsMachine LearningA/B TestingSystem DesignGenerative AIProduct SenseMetricsBehavioral
Browse all questions →Try a mock interview
Experiences
Practice
Mock InterviewsTimed interview simulations with feedbackCoaching1:1 coaching with people at your target companiesSuccess PathYour 6-week structured planModulesCurated lessons by topicWebinarsTalks from ex-Big Tech data leadsPlaygroundA free-form scratch editor
Learn
BlogInterview strategy and career adviceTech Job Market ReportHiring trends across data and AI rolesFor UniversitiesDataford for career centersAbout DatafordWho we are and how we build
Pricing
Build my plan
Optimize Slow SQL Queries
00:00
5 left

Optimize Slow SQL Queries

HardSQL · PostgreSQL

Problem

Walk me through how you would optimize a highly complex, slow-running SQL query used by the analytics team at Anduril Industries.

Using the provided PostgreSQL schema, produce an optimized query that preserves the required results. Consider filtering, join cardinality, aggregation strategy, latest-status selection, indexing, and how you would validate the improvement.

Output

  1. One row per completed mission starting before 2026-04-01
  2. Columns: mission_id, mission_name, asset_count, active_asset_count, critical_event_count, avg_signal_strength, and latest_status_at
  3. Sort by mission_id ascending

Schema

missions
ColumnTypeDescription
mission_idPKINTMission identifier
mission_nameVARCHAR(100)Mission name
mission_statusVARCHAR(30)Mission lifecycle status
start_atTIMESTAMPMission start timestamp
end_atTIMESTAMPMission end timestamp
mission_assets
ColumnTypeDescription
mission_idPKINTReferenced mission
asset_idPKINTReferenced asset
assigned_atTIMESTAMPAsset assignment timestamp
telemetry_events
ColumnTypeDescription
event_idPKINTTelemetry event identifier
asset_idINTReporting asset
occurred_atTIMESTAMPEvent timestamp
severityVARCHAR(20)Event severity
signal_strengthDECIMAL(6,2)Observed signal strength
asset_status_history
ColumnTypeDescription
status_idPKINTStatus history identifier
asset_idINTStatus asset
statusVARCHAR(30)Recorded asset status
recorded_atTIMESTAMPStatus timestamp
Tablesmissionsmission_assetstelemetry_eventsasset_status_history
Interviewer

Your question is Optimize Slow SQL Queries. Start with the requirements and the four tables 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.

You need to log in / sign up to run or submit.
CodePostgreSQL
Sign up free to run your codeLog inLn 1
Run your query to see results here.