#logs

10 logs interview questions, asked at Google, Amazon, Microsoft and 3 more companies. Last asked Sep 2026.

Find timed-out RPC calls from start and end logsCodingA service writes one log record when a remote procedure call starts and another when it ends, and the log is in time order. Given the log and a timeout, report every call that ran…
Last asked Sep 2026
Fast search over large autonomous-vehicle logsSystem designVehicles produce large raw logs and vehicle records. Design how engineers search them quickly, for example for every record that matches some conditions, when the data is far…
Last asked Aug 2026
Design log storage with live tailing of growing filesSystem designProducers keep appending records to log files at very high volume. Store them durably and let users read files back, including users who read a file while it is still being…
Last asked Aug 2026
Parse and summarize HTTP access logsCodingYou get log lines, each meant to hold an IP address, a timestamp, a URL or API path and a status code. Parse each line, decide whether it is valid, and report the total number of…
Last asked May 2026
Process login logs split across shardsCodingLogin records are spread across several shards. Combine them to answer questions about users' logins, merging the shards correctly and efficiently, and explain how your approach…
Last asked Apr 2026
Find when failures started in a logCodingA service writes a time-ordered log of request results, and at some point it started failing. Find the moment the failures began. Discuss the approach when you can only read the…
Last asked Jan 2026
Count errors in a log stream with a moving averageSystem designDesign a component that reads a continuous stream of log lines, counts errors per time window and keeps a moving average to spot spikes. Discuss windowing, memory bounds, late or…
Last asked Dec 2025
Find the first error in a log, then trace failures through dependenciesCoding1. A service's log lines are tagged Info, Warn or Error. Once the first Error appears the service is down, so every later line is an Error too, and the line just before the first…
Last asked Sep 2025
Count user sessions from an activity logCodingEach log line is timestamp, user, action. A session is a run of a user's actions with no gap longer than a given timeout. Return the number of sessions per user. Parse robustly…
Last asked Sep 2025
Filter and analyze logs with an object-oriented designOO designDesign classes that read a stream of log entries, some of them errors, filter them by rules such as level, time range or source, and report simple analytics such as error counts…
Last asked Sep 2025