# EvalFrame: Technical Interview Platform & Voice Mock Sparring
> Full-stack developer interview preparation platform pairing an 8-language code execution sandbox and relational database engine with real-time verbal mock interviews.

## Primary System Endpoints
- **Homepage & Architecture**: https://evalframe.com/
- **Mock Voice Interview Simulator**: https://evalframe.com/interview
- **Coding & SQL Problem Lab**: https://evalframe.com/practice

## Core Capabilities
- **Verbal Sparring Partner**: Real-time turn-by-turn spoken interviews with high-fidelity voice models and browser Web Speech API. Supports English, German, and French.
- **Dynamic Drill-Down Follow-Ups**: Probes specific technical claims, architecture choices, and trade-offs in real time to generate adaptive probing follow-up questions.
- **STAR Framework Hints**: Real-time coaching hints structuring answers into Situation, Task, Action, and Quantitative Result.
- **Polyglot Code Execution**: Monaco Editor sandbox supporting 8 languages: TypeScript, JavaScript, Python 3, Go, C++20, Java 17, Rust, and PHP.
- **In-Browser Database Sandbox**: Real relational SQL database execution inside a dedicated isolated Web Worker thread.
- **Edge Caching & Cloud Persistence**: Cloudflare Pages, D1 database persistence, and Cloudflare Edge Cache API for 0ms audio synthesis replays.

## Preset Technical Disciplines
1. **Senior Frontend Engineer**: Core Web Vitals, SSR hydration, state machines, Web Workers, CSS architecture.
2. **Staff Backend Architect**: High-concurrency distributed systems, Redis cache stampedes, idempotency, rate limiting, event queues.
3. **Fullstack Systems Engineer**: End-to-end API contracts, database schema migrations, auth pipelines, real-time WebSockets.
4. **DevOps & Cloud SRE**: Kubernetes failover, zero-downtime rolling deploys, Prometheus telemetry, infrastructure-as-code.
5. **System Design & Distributed Systems**: Sharding strategies, CAP theorem, consistent hashing, LSM-trees vs B-Trees, Kafka partitioning.
6. **Amazon STAR Behavioral**: Leadership principles, resolving engineering disagreements, post-mortem root-cause analysis, cross-functional delivery.
7. **Custom Role & Job Description**: Accepts any arbitrary job title and job posting description to synthesize company-specific interview sessions.

## Curated Problem Directory
- **Two Sum** (`02-two-sum`): Hash map complement lookup (O(N) time, O(N) space).
- **Valid Palindrome** (`01-palindrome`): In-place two-pointer scan (O(N) time, O(1) space).
- **Valid Parentheses** (`03-valid-parentheses`): Monotonic stack invariant matching (O(N) time, O(N) space).
- **Best Time to Buy & Sell Stock** (`07-best-time-to-buy-and-sell-stock`): Greedy single-pass (O(N) time, O(1) space).
- **Merge Sorted Arrays** (`10-merge-sorted-arrays`): Two pointers interleaving (O(N + M)).
- **Maximum Subarray** (`11-maximum-subarray`): Kadane's algorithm (O(N) time, O(1) space).
- **Second Highest Salary** (`sql-01-second-highest-salary`): In-browser SQL window function / offset query.
- **Duplicate Emails** (`sql-02-duplicate-emails`): SQL GROUP BY / HAVING clause execution.
- **Customers Who Never Order** (`sql-03-customers-who-never-order`): SQL LEFT JOIN with NULL filter.