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System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Technical Screen rounds at TikTok.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at TikTok during technical interviews.

Design a high-concurrency ticketing system

Quick Overview

This question evaluates a candidate's ability to design scalable, high-concurrency backend systems with strict inventory correctness, fairness, reservation/payment workflows, and operational concerns such as caching, message queues, consistency models, capacity planning, and load testing in the System Design domain.

Design a High-Concurrency Ticketing/Flash-Sale System (Limited Seats)

Context

You are designing the backend for a limited-seat flash sale (e.g., concert tickets). Millions of users may attempt to purchase simultaneously. The system must maintain strict correctness (no oversell), fairness, and resilience under extreme load, while supporting short reservations and payments.

Requirements

Scale and Correctness
- Handle millions of concurrent purchase attempts.
- No oversell; strict inventory correctness at seat or SKU level.
- Real-time availability exposure.
Fairness and Backpressure
- Provide fairness (FIFO queue or lottery).
- Queueing with backpressure and rate limiting.
Purchase Flow
- Short-term reservations with payment timeouts.
- Idempotent order creation and safe retries.
Reliability and Performance
- Anti-bot protections.
- Shard hot items.
- Describe read/write paths, caches/DBs, message queues.
- Consistency model and reconciliation.
- Failure handling.
- Capacity planning and load testing.

Deliverables

Describe the following:

APIs (endpoints, request/response sketches).
Data model (core entities and keys).
Read and write paths.
Cache/DB choices and where to use them.
Message queues and their topics/uses.
Consistency model, reconciliation strategy.
Failure handling and fallbacks.
Capacity planning assumptions and calculations.
Load testing methodology and SLOs.

Quick Overview

Requirements

Scale and Correctness

Handle millions of concurrent purchase attempts.
No oversell; strict inventory correctness at seat or SKU level.
Real-time availability exposure.

Fairness and Backpressure

Provide fairness (FIFO queue or lottery).
Queueing with backpressure and rate limiting.

Purchase Flow

Short-term reservations with payment timeouts.
Idempotent order creation and safe retries.

Reliability and Performance

Anti-bot protections.
Shard hot items.
Describe read/write paths, caches/DBs, message queues.
Consistency model and reconciliation.
Failure handling.
Capacity planning and load testing.

Deliverables

Describe the following:

APIs (endpoints, request/response sketches).

Data model (core entities and keys).

Read and write paths.

Cache/DB choices and where to use them.

Message queues and their topics/uses.

Consistency model, reconciliation strategy.

Failure handling and fallbacks.

Capacity planning assumptions and calculations.

Load testing methodology and SLOs.

Design a high-concurrency ticketing system

Quick Overview

Design a High-Concurrency Ticketing/Flash-Sale System (Limited Seats)

Context

Requirements

Deliverables

Solution

Comments (0)

Design a high-concurrency ticketing system

Quick Overview

Design a High-Concurrency Ticketing/Flash-Sale System (Limited Seats)

Context

Requirements

Deliverables

Solution

Comments (0)