Learn System Design Through a First-Come, First-Served Coupon Server
Build a first-come, first-served coupon issuance service and solve the problems that arise when requests surge, one by one. From watching the lectures to verifying course completion, join us for four weeks.
The challenge is free to join. Even those who haven't started taking the course yet can register.
What You'll Learn
More coupons may be issued than the prepared quantity, responses may be delayed, and some data may fail to be saved. You will reproduce these situations yourself, identify their causes, and then improve the design.
What happens when multiple requests come in for the same inventory? Compare database locks and Redis Lua, and learn how to enforce the issuance quantity and the one-per-person rule.
We find the sections where responses are delayed and separate the saving process using Kafka. We also address the problem of a surge in database queries when the cache expires.
We reprocess messages that failed to be saved and synchronize the records in Redis and MySQL. We apply a waiting room and request limits so the server only accepts as many requests as it can handle.
4-Week Curriculum
Each week, watch approximately 2–3 hours of lectures and upload a screenshot of the completion screen for that section. You will continue developing a single coupon service while addressing concurrency, caching, and consistency issues in sequence.
Set up the practice environment and implement coupon creation, issuance, and lookup features. Use a database unique constraint to prevent duplicate issuance to the same user.
Reproduce over-issuance with k6 and compare DB locks with Redis Lua. Then apply Kafka to separate user responses from database storage.
Measure the load that repeated queries place on the server. Apply Single Flight and SWR to reduce the surge of requests to the DB when the cache expires.
We recover messages that failed with the DLT and synchronize the data in Redis and MySQL. We prepare for situations where requests flood in all at once with a virtual waiting room and a rate limiter.
The learning mission is to certify that you have completed each week's lessons.
Just watch the assigned content and upload a screenshot of the completion screen. There are no separate assignments to submit or code reviews.
The above time is based on watching the videos. Additional time is needed for hands-on practice.
Your own creation results
We implement the entire flow of receiving requests, checking inventory, and storing issuance records. We apply the same load to compare response times and error rates, and also check the number of items issued and any missing records.
The course is conducted with Kotlin and Spring Boot, and the practice code is provided in both Kotlin and Java versions. MySQL, Redis, and Kafka are run using Docker Compose.
Recommended for
You should be familiar with HTTP and REST APIs, basic SQL, and Java or Kotlin syntax. Experience building APIs with Spring Boot is a plus. It’s okay if you’re new to Redis and Kafka.
Participation Guide
Whether you’re already taking the course or just getting started, you can participate. If you haven’t enrolled yet, register for the challenge first, then check the discount coupon information below.
Complete the course and receive a certificate.
By organizing your implementation code and load testing results, you can use them as a portfolio that explains the design process.
FAQ
Yes, you can participate regardless of your current progress. Start with the Week 1 mission and verify that you have completed the prescribed amount of the course.
Yes. The course is taught in Kotlin, and you can also find Java source code in the course materials.
If you have experience with Java and Spring, you’ll be able to follow along. Any necessary Kotlin syntax is explained during the hands-on exercises as well.
The Controller, Service, and DI structure is similar, so you can leverage your existing backend experience. You can also learn unfamiliar syntax and concepts with the help of AI.
For those who have not yet taken the course
After registering for the challenge, please submit your pledge to the mission before the challenge begins. We will give you a 30% discount coupon that can be used for the companion course.
