今日固定时间表
三块窗口固定：08:50-10:55 系统设计，14:30-16:15 算法，20:30-21:15 口述。
| 08:50-09:10 | 08:50-10:55 system design 闭卷建模 - 写 Event/Venue/Ticket/Hold/Booking/PaymentAttempt；标出哪些是 source of truth。 |
|---|---|
| 09:10-09:45 | 08:50-10:55 system design 精确原文 - 读 Ticketmaster 从 Understanding the Problem 到 High-Level Design 的全部 required anchors。 |
| 09:45-10:25 | 08:50-10:55 system design 白板主路径 - select seat -> reserve hold -> checkout -> payment webhook -> conditional held->sold。 |
| 10:25-10:55 | 08:50-10:55 system design DDIA 决策卡 - 用 Ch8 条件写入和多对象事务定义 reserve/confirm 的线性化点。 |
| 14:30-16:15 | NeetCode Tag · Binary Search 三道题，每题 30m solve + 5m evidence，不能改 tag。 |
| 20:30-21:15 | 20:30-21:15 Ticketmaster English recall：source of truth, reserve, expiry, payment idempotency, oversell prevention。 |
算法模块
连续 NeetCode Binary Search；每天 exactly 3 slots。
| # | Problem / mode | Pattern | Invariant | Bug risk | Time | Space |
|---|---|---|---|---|---|---|
| 1 | Binary Search NEW · 30m solve + 5m evidence | closed interval binary search | target, if present, remains inside [lo, hi]. | Infinite loop from mid bias or lo/hi update that does not shrink. | O(log n) | O(1) |
| 2 | Search Insert Position NEW · 30m solve + 5m evidence | lower_bound | lo is the first possible insertion index after each shrink. | Returning hi after an exclusive upper-bound loop without checking convention. | O(log n) | O(1) |
| 3 | Guess Number Higher Or Lower NEW · 30m solve + 5m evidence | monotone predicate | The answer is inside the remaining numeric range. | Overflow in mid; reversing higher/lower branch. | O(log n) | O(1) |
Hello Interview 精确目录
保留 live canonical heading title；day page 使用 direct section anchors。
| 项目 | 精确 canonical section | Disposition | 今天怎么用 |
|---|---|---|---|
| Ticketmaster | Understanding the Problem | required reading | define the product and the scarce resource: event seats |
| Ticketmaster | Functional Requirements | required reading | view events, search events, book tickets |
| Ticketmaster | Non-Functional Requirements | required reading | available reads, consistent booking, hot-event throughput, low-latency search |
| Ticketmaster | The Set Up | required reading | interview framing before design |
| Ticketmaster | Planning the Approach | required reading | requirements to entities to API to HLD |
| Ticketmaster | Defining the Core Entities | required reading | Event, User, Performer, Venue, Ticket, Booking |
| Ticketmaster | API or System Interface | required reading | view/search/booking APIs that evolve into reserve and confirm |
| Ticketmaster | High-Level Design | required reading | read services plus booking service and payment processor |
| Ticketmaster | 1) Users should be able to view events | required reading | event detail and seat map projection |
| Ticketmaster | 2) Users should be able to search for events | required reading | search service and low-latency read path |
| Ticketmaster | 3) Users should be able to book tickets to events | required reading | no-double-booking transaction path |
DDIA 精确决策卡
只使用 Ch8 和 Ch10 中直接解决今天设计决定的小节。
| 项目 | 项目问题 | 精确 DDIA subsection | 改变的系统决定 |
|---|---|---|---|
| Ticketmaster | A seat hold succeeds at exactly which write, and why does a duplicate reserve fail? | Ch8 - 条件写入（比较并设置） | Reserve uses a conditional write on seat/hold version; retry returns the existing hold or a rejected stale-version result. |
| Ticketmaster | Can booking multiple seats commit half the order? | Ch8 - 单对象与多对象操作 | Multi-seat purchase is one order transaction or a saga with explicit partial-release compensation; no silent half-sold set. |
三域 trace 任务
Winning transaction标出唯一线性化点：seat hold/sold、accepted bid at close、brokerage order/execution state。
Duplicate/retry failure给出 stable idempotency key、重复返回语义、旧 owner/stale version 被拒绝的证据。
Projection boundary说明哪些读可以陈旧：seat map、highest bid display、market price UI；哪些写不能陈旧。
本日 artifacts
项目脚本、音频、PDF 和 mock evidence 从当天直接打开。
今日产出、修复与英语 recall
| 课程角色 | CORE · requirements/API/data model/HLD |
|---|---|
| 必须交付 | Ticketmaster HLD：seat/hold/order/payment 状态机，reserve 与 confirm 两个 API，winning seat transaction trace。 |
| 修复规则 | 如果把 seat-map cache 当成可购买事实，重画 cache projection 与 authoritative inventory 的边界。 |
| English recall | English recall: A seat-map read can be stale; only the conditional hold or sold transition decides ownership. |
Detailed lecture notes, audio, recall scripts, PDFs, Staff Q&A, and mock packs are archived locally and are intentionally not published on this site.