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Implement log storage and querying

DatadogSoftware Engineer · Technical Screen
MediumSoftware EngineerTechnical ScreenCoding & Algorithms

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This question evaluates a candidate's skill in designing and analyzing log storage and query systems, covering data layout, indexing strategies, time-range scans with optional filters, and time/space complexity reasoning.

Design a data structure to record log entries and support efficient queries. Each log has a timestamp (milliseconds), severity (INFO/WARN/ERROR), serviceId (string), and message (string). Support:

  1. append(log),
  2. count(startTime, endTime, filters), and
  3. get(startTime, endTime, filters, orderBy, limit, offset). Describe your data layout, indexing strategy, and how you handle time-range scans plus optional filters on severity and serviceId. Provide expected time and space complexity for each operation and discuss trade-offs between write amplification and query latency.