Google Software Development Engineer Interview Questions (2026)

1. 1Recruiter screen30 minEasy

   Background, level calibration, and process walkthrough with a recruiter.

2. 2Technical phone screen45 minHard

   One or two DSA problems solved live in a shared editor with emphasis on optimal complexity and clean code.

3. 3Coding round (onsite)45 minHard

   Harder DSA with follow-up constraint changes; interviewer scores GCA and RRK on a rubric.

4. 4System design round45 minHard

   Design a planet-scale system (e.g. a piece of Search or YouTube) with explicit capacity estimates and tradeoffs.

5. 5Googleyness & Leadership45 minMedium

   Behavioral round on collaboration, ambiguity, and user-first judgment scored against Google's structured rubric.

6. 6Hiring Committee review30 minMedium

   No candidate interaction; the written feedback packet is reviewed and the hire/no-hire decision is made, followed by team matching.

1. Q1

   In a clean-design discussion, answer this: Design classes for assigning YouTube users to experiments

   MediumLow Level DesignA/B experiment SDK

   How to answer:

   Model Experiment, Variant, Allocation, EligibilityRule, AssignmentService, and ExposureLogger; use deterministic hashing and log exposures once. Keep APIs small, invariants explicit, and tests first-class.

2. Q2

   For an L5+ style open-ended design round, answer this: Design an experimentation platform for Search

   HardHigh Level DesignA/B testing platform

   How to answer:

   Use deterministic assignment, experiment config service, exposure logging, metrics pipeline, guardrails, and analysis dashboards; handle mutually exclusive experiments. Call out SLOs, bottlenecks, and data consistency.

3. Q3

   In a clean-design discussion, answer this: Design a reusable API client for Gmail with auth refresh and request signing

   HardLow Level DesignAPI client with auth

   How to answer:

   Separate HttpClient, AuthProvider, TokenStore, RequestSigner, RetryPolicy, and Serializer; refresh tokens safely and avoid logging secrets. Keep APIs small, invariants explicit, and tests first-class.

4. Q4

   For an L5+ style open-ended design round, answer this: Design an API gateway for Photos backend services

   HardHigh Level DesignAPI gateway

   How to answer:

   Handle auth, routing, rate limits, request validation, retries/timeouts, observability, and versioning. Keep business logic out of the gateway. Call out SLOs, bottlenecks, and data consistency.

5. Q5

   Clarify assumptions, talk through examples, then solve this: Code a mapper from a raw YouTube API response to a stable internal model

   MediumCodingAPI response mapper

   How to answer:

   Validate required fields, provide defaults for optional fields, isolate external schema changes, and test unknown fields and backward compatibility. Explain before coding and state Big-O.

6. Q6

   For an L5+ style open-ended design round, answer this: Design an ad-serving system for Maps

   MediumHigh Level DesignAd serving

   How to answer:

   Separate request routing, candidate retrieval, auction/ranking, budget pacing, frequency capping, logging, and fraud detection; optimize p99 latency. Call out SLOs, bottlenecks, and data consistency.

7. Q7

   In a clean-design discussion, answer this: Design a low-level audit logger for Ads administrative actions

   MediumLow Level DesignAudit log component

   How to answer:

   Model AuditEvent, Actor, Target, Metadata, Sink, and Redactor; ensure append-only semantics and safe handling of PII. Keep APIs small, invariants explicit, and tests first-class.

8. Q8

   Clarify assumptions, talk through examples, then solve this: Find the minimum number of connections between two users/devices/items in Ads

   HardDSABFS shortest hops

   How to answer:

   Use BFS from the source, marking visited nodes and parent if path is needed. O(V+E); consider bidirectional BFS for large graphs. Explain before coding and state Big-O.

9. Q9

   Clarify assumptions, talk through examples, then solve this: Implement a batcher for Maps events that flushes by size or time

   MediumCodingBatching helper

   How to answer:

   Buffer events, flush when max size or max age is reached, make flush thread-safe, and test empty, timer, size, and failure behavior. Explain before coding and state Big-O.

10. Q10

    For an L5+ style open-ended design round, answer this: Design CDN and origin protection for YouTube static assets

    MediumHigh Level DesignCDN origin shielding

    How to answer:

    Use multi-tier caching, signed URLs, cache keys, origin shield, purge pipeline, health checks, and logs for cache hit-rate analysis. Call out SLOs, bottlenecks, and data consistency.

11. Q11

    Clarify assumptions, talk through examples, then solve this: Implement a CSV reader for Android export files with quotes and escaped quotes

    HardCodingCSV reader

    How to answer:

    Use a state machine over characters; handle quoted fields, delimiters, newlines in quotes, and escaped quotes; test malformed rows. Explain before coding and state Big-O.

12. Q12

    In a clean-design discussion, answer this: Design a configurable cache library for Search clients

    MediumLow Level DesignCache library

    How to answer:

    Expose Cache<K,V>, EvictionPolicy, ExpiryPolicy, Loader, and Metrics; support LRU/LFU/TTL while keeping thread-safety and testing clear. Keep APIs small, invariants explicit, and tests first-class.

13. Q13

    For Google's Gmail notification delivery flow, write production-quality backend code to normalize cache keys and add negative caching for not-found results while meeting a 150 ms p99 target. Describe the main function or class interface, the core data structures, and the edge cases you would test

    HardCodingCaching

    How to answer:

    A strong answer proposes a small, testable interface and uses canonical key construction, TTL tiers, and explicit invalidation hooks. It handles retries, invalid input, timeouts, and cleanup explicitly, and states O(1) key lookup with reduced origin load.

14. Q14

    In a Google backend interview, solve this DSA problem from Calendar availability: choose objects for eviction under size and value constraints. Provide the algorithm, prove correctness, and analyze complexity under 100k events per second

    HardData Structures & AlgorithmsCaching

    How to answer:

    Model the problem with knapsack approximation or greedy by value/size depending on constraints. The target solution should achieve O(nW) exact pseudo-polynomial or O(n log n) greedy, handle empty inputs and ties, and explain why simpler brute-force approaches do not scale.

15. Q15

    Design cache-aware read APIs with explicit cache-control semantics and invalidation hooks for Google's Ads auction pacing read/write workflow. Specify endpoints or RPCs, request and response schemas, error handling, authentication, idempotency, and pagination where relevant

    MediumAPI DesignCaching

    How to answer:

    A strong answer defines resource-oriented REST endpoints or clear RPC methods for create, retrieve, update, list, and audit operations. It includes stable identifiers, authorization boundaries, validation rules, explicit error codes, rate limits, and backward-compatible versioning.

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Master DSA and communicate your thinking out loud; use Google's structured Explain-Clarify-Improve approach; prepare for Googleyness/behavioral

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