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They're grouped by theme so you can target your practice efficiently.

1. Coding & Algorithms (15 questions)

Load-Balancing Split

Given an array where each element is the CPU time of a task, partition the tasks between two cores so that the absolute difference in total time is minimized. Return the minimum difference.

Generative Cache

Implement an LRU cache that triggers an asynchronous regeneration callback when an item is evicted. All operations must be O(1) average time.

Immutable Merge Intervals

You receive a read-only list of time intervals (huge, memory-mapped). Find the minimum number of intervals to remove so the rest are non-overlapping—without modifying the original list.

Dynamic K-Nearest Stream

Maintain the k closest geographic points to (0, 0) in a real-time IoT stream that can burst to 10 million events / second.

Homomorphic Sum

Write a function that computes the sum of two encrypted integers represented with the Paillier cryptosystem without decrypting them.

DNA Assembly

Reconstruct the shortest super-string from an array of DNA fragments; discuss trade-offs between greedy vs. DP solutions when length more than 2000.

Concurrent Trie Delete

Extend a thread-safe trie to support delete(word) while other readers may be traversing; no global lock allowed.

Median of Sliding Window (k = 10^5)

Optimize both memory and CPU; discuss why a dual-heap may thrash caches at this size.

Sparse Matrix Rotation

Rotate a huge sparse matrix 90° clockwise in-place on disk; CRS format is required.

Circular Dependency Resolver

Detect and break the minimum number of edges in a directed graph representing micro-service calls so the graph becomes acyclic.

Encrypted Binary Search

On a list of integers encrypted with order-preserving encryption, implement binary search and analyze leakage.

Robot Path with Energy Refill

Find the least-cost path in a grid where each cell may recharge or drain energy; robot dies if energy is less than 0 at any step.

Versioned Union-Find

Add time-travel queries—"Were u and v connected at timestamp t?"—to a standard disjoint-set structure.

Latency Histogram Merge

Merge two HDR histograms into one without losing percentile accuracy.

Dynamic Range Bitset

Design a bitset supporting set(i), clear(i), and rank(i) for i up to 10^12, with ≤ 2 GB RAM.

2. System Design (10 questions)

Edge Generative-AI Service

Design a low-latency image-generation API that runs models partly on-device and partly in the cloud. Discuss model-split strategy, cache reuse, and billing.

Real-Time Fraud Graph

Build a system to flag suspicious transactions within 300 ms using streaming graph analytics over 500 K events / s.

Privacy-Sandbox Ads Pipeline

Architect a contextual-ads service that complies with Privacy Sandbox (Topics API) and regional data-residency rules.

Global Feature Store

Design a multi-tenant feature store that guarantees p95 is less than 10 ms reads across three continents. Address freshness and backfills.

Serverless ETL Orchestrator

Outline a DAG scheduler for event-driven ETL that can fan-out 1000+ lambdas yet enforce data-lineage recording.

Zero-Trust API Gateway

How would you architect an API gateway that enforces per-request device posture checks and mutual TLS?

Live-Streaming Chat with Moderation

Design a chat subsystem for live video where messages must appear under 200 ms and pass ML toxicity filters.

Blockchain Rollup Explorer

Build an explorer for optimistic rollups that indexes blocks, proofs, and fraud challenges in near real-time.

ML Experiment Tracker at Scale

Provide versioning, lineage, and artifact storage for thousands of concurrent model training jobs.

AI-Assisted Coding Platform

Architect a collaborative IDE in the browser that streams code-completion suggestions while preserving user privacy.

3. Cloud & Scalability (5 questions)

Hot-Key Mitigation

Your key-value store sees a 99 : 1 read skew. Propose three mitigation techniques and deep-dive on one.

Cost-Aware Autoscaling

Design an autoscaler that factors in spot-instance prices and carbon intensity of regions.

Multi-Region Failover Drill

Walk through the run-book and control-plane changes to execute an active-active failover in under 5 minutes.

Edge-Cache Purge Protocol

Create a protocol to invalidate cached content worldwide within 30 seconds while preventing replay attacks.

Observability Pipeline

How would you collect, compress, and query 15 TB/day of logs with 30-second query p95?

4. Front-End & User Experience (5 questions)

Reactive 3-D Dashboard

Describe how you'd render a real-time 3-D network map in React / WebGL at 60 FPS on mid-range laptops.

Privacy-First Analytics

Build a client-side analytics SDK that hashes PII locally and supports differential privacy.

Offline-First PWA

Design the caching strategy and data-sync conflict resolution for a progressive web app used on spotty rural networks.

Accessibility Heuristics Engine

Implement runtime checks that flag WCAG 2.2 violations during component rendering.

Rendering Large Lists

Compare virtualization libraries and propose your own strategy for rendering a list of 1 million items with dynamic row heights.

5. Machine Learning & Data (5 questions)

RAG (Retrieval-Augmented Generation) Tuning

How would you evaluate retrieval recall vs. generation faithfulness in a RAG pipeline serving customer-support answers?

Concept Drift Detection

Design an online algorithm to flag drift in a credit-scoring model within an hour of distribution shift.

Federated Learning Pipeline

Architect a mobile federated-learning system that trains on-device, aggregates server-side, and enforces Secure Aggregation.

Vector-Database Sharding

Choose a sharding strategy for a 5-B-vector store powering semantic search; discuss recall impact.

Synthetic Data Generation Guardrails

How would you ensure synthetic tabular data preserves correlations but strips re-identification risk?

6. DevOps, SRE & Reliability (5 questions)

AI-Ops Incident Triage

Propose a pipeline that clusters alerts, predicts incident severity, and suggests run-book actions automatically.

eBPF Observability Rollout

Plan a staged rollout of eBPF tracing in production without exceeding 5 % CPU overhead.

Chaos Engineering Game Day

Design a game-day scenario to test a payment service's idempotency and rollback guarantees.

SLO Budget Alerts

You have an SLO of 99.95 %. Describe how to compute and act on error-budget burn-down in real time.

Secure Supply-Chain Build

Integrate Sigstore and SBOM checks into a GitHub Actions CI/CD workflow to prevent dependency attacks.

7. Behavioral & Leadership (5 questions)

Culture Add, Not Fit

Tell us about a time you challenged an entrenched engineering norm and what changed because of it.

Leading Through Ambiguity

Describe how you drove clarity on a project with shifting executive goals and no clear owner.

Fail-Fast Story

Give an example where killing a prototype early saved resources. How did you decide and communicate it?

Mentoring Across Time Zones

How have you grown junior engineers who work 8+ hours offset from you?

Ethical Stand

Recall an incident where you flagged a potential ethical or privacy concern in product design. What was the outcome?

How to Use This List

Self-diagnose weak areas:Color-code which questions you could answer today vs. ones that stump you.
Simulate full loops:Pick 1–2 from each section to create realistic 60-minute practice sessions.
Deep dive, don't memorize:Understand trade-offs, articulate assumptions, and relate choices to user impact.

Master these patterns—and the reasoning behind them—and you'll walk into your 2025 interviews prepared for whatever curveballs the panel throws.

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