System designLast seen Oct 2026
Design an Exact User-ID Membership Store
Support exact membership and atomic add-if-absent over one million IDs under contrasting memory budgets.
Open practiceMercor interview practice
Mercor interview questions and coding practice Start with verified evidence.
Practice from 10 Mercor-tagged public coding problems, organized only by the stage, topic, difficulty, and recency metadata FastPrep can verify. The broader public catalog also includes 10 system-design exercises, 3 project-coding exercises.
- Catalog
- 23 public practice assets (10 coding)
- Start here
- Use the stage named in your invitation
- Evidence
- Phone · Onsite metadata, shown in context
Phone practice path
Phone Screen
Practice solving while explaining assumptions, tradeoffs, and complexity. Problems are ranked by repeated public catalog sightings.
5 Mercor-tagged Phone Screen problems available.
| Company | Problem | Difficulty | Public evidence | Action |
|---|---|---|---|---|
MEMercor | Sort by Checking PermutationsArrayBacktracking | Easy | 2 public reportsLast reported Oct 2026 | Practice |
MEMercor | Coffee Rank ProbabilityMathCombinatorics | Easy | 1 public reportLast reported Oct 2026 | Practice |
MEMercor | CSV Row SerializerStringParsing | Medium | 1 public reportLast reported Sep 2026 | Practice |
MEMercor | Process Refunds with Bounded RetriesSimulationArray | Easy | 1 public reportLast reported Sep 2026 | Practice |
MEMercor | Shortest Path in a Grid with Obstacles EliminationMatrixBreadth-First Search | Hard | 1 public reportLast reported Sep 2026 | Practice |
Onsite practice path
Onsite
Practice complete solutions and defend the choices behind them. Problems are ranked by repeated public catalog sightings.
| Company | Problem | Difficulty | Public evidence | Action |
|---|---|---|---|---|
MEMercor | Top K With a Deterministically Noisy Comparator (MLE)ArraySorting | Hard | 2 public reportsLast reported Sep 2026 | Practice |
MEMercor | Merge Sort Report with a Noisy ComparatorArraySorting | Medium | 1 public reportLast reported Sep 2026 | Practice |
MEMercor | Minimum Friend API CallsGraphBreadth-First Search | Medium | 1 public reportLast reported Sep 2026 | Practice |
MEMercor | Park Train Cars by PreferenceGraphDepth-First Search | Medium | 1 public reportLast reported Sep 2026 | Practice |
MEMercor | Currency Conversion RateGraphBreadth-First Search | Medium | 1 public reportLast reported Sep 2026 | Practice |
01 · Preparation plan
Turn graph search, noisy ranking, and durable orchestration into a deliberate practice loop.
Mercor's mixed catalog supports a progression from bounded algorithmic state to uncertain comparisons and then to dependable work execution across unreliable workers. Catalog labels guide practice but do not promise a current or universal hiring loop. This is a suggested practice sequence, not the employer's interview process. Your invitation and recruiter guidance remain the source of truth.
- 01
Practice Shortest Path in a Grid with Obstacles Elimination
Use Shortest Path in a Grid with Obstacles Elimination to rehearse state-augmented breadth-first search. Keep the exercise's published contract separate from assumptions about Mercor's current interview process.
- Restate the exact input, output, and constraints for state-augmented breadth-first search.
- Explain the data structure and complexity before completing the implementation.
- Test a boundary case, a repeated-value case, and the smallest valid input.
- 02
Practice Top K With a Deterministically Noisy Comparator
Use Top K With a Deterministically Noisy Comparator to rehearse ranking under an unreliable comparator. Keep the exercise's published contract separate from assumptions about Mercor's current interview process.
- Restate the exact input, output, and constraints for ranking under an unreliable comparator.
- Explain the data structure and complexity before completing the implementation.
- Test a boundary case, a repeated-value case, and the smallest valid input.
- 03
Practice Design a Durable Work Orchestration Platform
Use Design a Durable Work Orchestration Platform to rehearse durable workflows, retries, and backpressure. Keep the exercise's published contract separate from assumptions about Mercor's current interview process.
- Set concrete scale, latency, and correctness requirements for durable workflows, retries, and backpressure.
- Draw ownership boundaries and the data path before choosing components.
- Exercise one overload or dependency failure and explain the recovery path.
02 · Broader technical practice
Practice beyond standalone coding questions.
These public Mercor-tagged exercises cover additional technical formats. They are included only when a verified catalog record and a crawlable practice page both exist.
Project codingLast seen Oct 2026
Repair CSV Construction
Repair quadratic CSV assembly and extra row-ending delimiters.
Open practiceProject codingLast seen Oct 2026
Repair Idempotent Payment Processing
Repair database ordering and safe reconciliation around payment-provider uncertainty.
Open practiceSystem designLast seen Oct 2026
Design an Online Payment Processing System
Design a reliable payment path that turns an order into one captured charge and reconciles uncertain provider outcomes.
Open practiceSystem designLast seen Oct 2026
Design a Durable Work Orchestration Platform
Design a durable, tenant-fair workflow control plane for fast I/O and slow LLM tasks, with quota-aware dispatch, resumable progress, asynchronous waits and reliable stream-to-result commits.
Open practiceSystem designLast seen Sep 2026
Design a Dataset Copy API
Copy a consistent dataset snapshot across workspaces with asynchronous progress, integrity verification, and atomic publication.
Open practiceSystem designLast seen Sep 2026
Design a Persistent Multi-Thread AI Chat
Let an authenticated user start a new chat or reopen a previous thread and stream the next assistant reply from durable history.
Open practiceSystem designLast seen Sep 2026
Design Context Window Management for an AI Assistant
Keep a long-running assistant grounded when durable conversation history no longer fits in one model request.
Open practiceSystem designLast seen Sep 2026
Design Prompt Injection Defenses for an AI Agent
Contain instructions hidden in untrusted content before an agent can use sensitive data or invoke side-effecting tools.
Open practiceProject codingLast seen Sep 2026
Repair a Concurrent Read-Through Cache
Prevent duplicate expensive work without serializing hits or unrelated keys.
Open practiceSystem designLast seen Aug 2026
Design a Project-to-Contractor Matching Platform
Design a platform that turns project requirements and contractor profiles into timely, explainable, and eligibility-safe ranked shortlists.
Open practiceSystem designLast seen Aug 2026
Design a Unique Username Registration System
Design a registration service that assigns each normalized username to at most one account under both memory-rich and disk-constrained deployments.
Open practiceSystem designLast seen Jun 2026
Design an External Career Data Analytics Platform
Design a governed data platform that preserves external career records, publishes joinable historical models and aggregates, and serves trustworthy stakeholder dashboards.
Open practice03 · Evidence boundary
What “Mercor interview questions” means here.
It means practicing transferable implementation, testing, and technical reasoning with public catalog assets FastPrep tags to Mercor. It does not mean FastPrep has access to the company's assessments or any private interview bank.
Repeated public sightings and last-reported dates can help you prioritize practice, but they cannot predict the questions, format, or platform in a specific interview.
- Only Mercor-tagged FastPrep catalog problems appear above.
- Stage labels and report dates remain visible as context.
- No official, private, leaked, or proprietary questions are claimed.
04 · Plain answers
Mercor interview practice questions, answered plainly.
This page owns technical-practice intent for Mercor. Hiring activity, timelines, and market signals remain on the separate hiring-insights page.
01What evidence supports this Mercor interview practice page?
The launch review verified 2 coding exercises, 4 system-design exercises (6 total public practice items). The strongest reviewed themes are state-augmented breadth-first search, ranking under an unreliable comparator, durable workflows, retries, and backpressure. Counts and report labels can change, so use this as a focused practice library and follow your own invitation for the current format, timing, and permitted tools.
02Is FastPrep affiliated with Mercor?
No. FastPrep is an independent interview-preparation product and is not affiliated with Mercor. The page uses FastPrep's public practice catalog and does not claim official, private, leaked, or proprietary employer questions.
03How are Mercor problems assigned to interview stages?
Stage labels come from FastPrep's public problem metadata. A problem can carry more than one reported stage, and hiring processes can change by role, level, location, and date. Treat the labels as preparation context, not a guarantee.
04Which Mercor interview stage should I practice first?
Start with the stage named in your invitation or recruiter message. If no stage is known, use the largest available set to build general problem-solving fluency, then rehearse explanation and testing separately.
05Does this page predict the Mercor interview process?
No. Public catalog counts, stage tags, and last-reported dates can help prioritize practice, but they cannot predict a specific interview's questions, sequence, timing, or platform.
Your next stage, made concrete
Pick a problem. Solve it end to end.
Start with the stage named in your invitation, then use public evidence as context—not as a promise of what you will be asked.
Open the practice set