## Task Management System (in-memory) Design and implement an in-memory task management system that supports tasks, users, task assignment with TTL (time-to-live), and time-based completion/expiration rules. ### Entities - **Task**: `id` (unique), `name`, `priority` (higher number = higher priority, or clearly define). - **User**: `id` (unique), and a **quota** = maximum number of **active task assignments** the user may have at once. - **Task Assignment**: assigns a task to a user at a `startTime`, with a `ttl` (duration). The assignment is **active** on `[startTime, startTime + ttl)` and **expired** at or after `startTime + ttl`. ### Requirements / APIs 1. **Task CRUD** - Create a task. - Get a task by id. - Update a task (e.g., name/priority). 2. **Task listing** - Return the top **N** tasks by priority. - Return the top **N** tasks by priority **whose name contains a given substring**. 3. **Users + assignment with TTL** - Add a user with a quota. - Assign a task to a user with a TTL at a given `startTime`. - You may assign **multiple tasks to the same user**. - You may assign the **same task to multiple users**. - (If the same task is assigned multiple times to the same user at different start times, treat them as distinct assignments.) - List a user’s **active** tasks at a given time `t`. 4. **Completion + expiration rules** - Complete a task for a user at a given time `t`. - You **cannot** complete an **expired** assignment. - If there are **multiple active assignments** for the same `(userId, taskId)`, completing that `taskId` completes the one with the **earliest startTime**. - List a user’s **expired** tasks at a given time `t`. ### Clarifications to state during the interview - How ties in priority are broken (e.g., higher priority first, then by `taskId` lexicographically). - Whether “list tasks by priority” returns **tasks** (unique by taskId) or **assignments** (can repeat taskId). (Common approach: listing in (2) is over tasks; user lists in (3)/(4) are over assignments.) - Input constraints and expected complexity (aim for efficient queries; in-memory only).