
Spring Core Principles - Basic Edition
yh
$68.20
Basic / Spring, oop
5.0
(4,913)
50,300+
Spring beginners can grasp core principles and solidify basics via examples.
Basic
Spring, oop
"A query that ran perfectly during development suddenly slows down as data accumulates." At such times, the mark of a truly skilled developer is identifying the root cause based on solid evidence rather than guesswork, and optimizing a 30-second query down to 0.1 seconds. Master the core principles of database performance—from execution plans, indexes, and optimizers to joins and sorting—using millions of rows of real-world data. Elevate your skills and become a top-tier developer capable of independently analyzing and resolving slow queries in production environments.
1,924 learners
Level Intermediate
Course period Unlimited
Reviews from Early Learners
5.0
박종철
Hello. I sincerely congratulate you, Kim Young-han, on completing your incredible 7-year journey! I have been taking your classes ever since my first one in January 2023, eagerly waiting for the notifications of new course releases to pop up. Looking back now at those late-night study sessions after work, rubbing my sleepy eyes to stay awake, I sometimes wonder how I managed to keep at it. It was grueling and a bit daunting, but it also filled me with immense pride and happiness. It has been a tremendous privilege and a source of great pride to have accompanied you to the very end of this monumental journey, one in which you poured your heart and soul into every meticulous detail. Once again, thank you from the bottom of my heart for tirelessly completing this remarkable roadmap over the past 7 years.
5.0
이수현
When I was preparing for employment, I used to be amazed by how easy it was to understand Mr. Kim Young-han’s lectures. They also helped strengthen my determination to find a job and motivated me to work hard in my preparation. Now that I’m employed, I’ve reached the stage where I think not only about basic database design but also about performance optimization. Even as I continue gaining hands-on experience, I’m very happy and grateful to still be learning alongside Mr. Kim Young-han’s lectures. Studying while envisioning an actual production database seems to make the lectures even more helpful. Thank you so much, as always, for your excellent lectures.
5.0
widn45
You explained MySQL so clearly! Thank you.
The ability to read an execution plan and independently diagnose the cause of a slow query.
The ability to independently design indexes tailored to specific situations.
Real-World Experience in Optimizing Queries by 10x to 100x Across Millions of Data Records
Understanding Database Internals Beyond Indexes
Kim Young-han's Practical Database
Members 3 million, products 5 million
The service is growing day by day, but
is it getting slower and slower?!
Amidst the vast sea of data, the queries that have become bottlenecks...
How can we solve this?
If you've hit the fundamental limits of database performance
An accurate diagnosis and tuning strategy is
required.
That's why we prepared
The final step in learning databases is,
ultimately, performance.
Once you learn how to write queries, you'll inevitably hit the same wall.
'I definitely wrote it correctly, so why is it so slow?'
This is exactly why we chose performance optimization as the final topic of the database roadmap.
Once you see with your own eyes how queries are actually executed and why indexes are so fast,
only then can you truly say you know how to properly handle databases.
With a solid guide tailored to real-world practice, we will help you complete the final step of your database journey.
By taking this course,
I created an index, but why does the optimizer ignore it?
Even when it hits the index perfectly, why is it still slow?
EXPLAIN results, where should you start reading?
Can a single join order turn 0.01 seconds into 22 seconds?
Why does it suddenly slow down just by adding ORDER BY?
As you paginate further, why does it get progressively slower?
POINT 1
Uncover the true cause of slow queries and resolve them by applying fundamental principles.
STEP 01
Understand how queries are executed internally within the database, and accurately diagnose the causes of performance bottlenecks using EXPLAIN and EXPLAIN ANALYZE.
STEP 02
Understand why indexes are fast through the B+Tree structure and identify why they can still be slow even when used, enabling you to design composite and covering indexes.
STEP 03
Learn how to resolve performance issues across various query types, from retrieval and search to joins, sorting, paging, and grouping.
POINT 2
Imagine you've just joined a rapidly growing e-commerce company.
This course is designed to help you develop practical skills by tackling various performance issues you'll encounter in the field,
building your real-world expertise.
4 Hands-On Tuning Exercises to Solve Problems Using the Principles You've Learned
Tuning 01 · Execution Plan
🛒 Admin Order Inquiry
Quickly retrieve only the necessary data with a composite index
We diagnose the full scan of 10 million rows using EXPLAIN and optimize the query to read only the necessary rows.
Tuning 02 · Sorting
🔍 Product Search
Eliminate the sorting operation itself using index sort
Eliminates the filesort operation that re-sorts data for every ORDER BY clause by using an index sort.
Tuning 03 · Join
📊 Order Statistics by Member
Covering index fetches all data in a single pass without revisiting the original table
Eliminates the bottleneck of re-fetching the original data on every join by leveraging a covering index.
Tuning 04 · Grouping
⭐ Review Rating Aggregation
Index sort for direct aggregation without a temporary table
Eliminate the temporary table created by GROUP BY using index sorting to aggregate directly.
Roadmap
This course is a follow-up to Youngjae Kim's Practical Database Roadmap, covering how to diagnose performance issues encountered in large-scale services using execution plans and resolve them with indexes.
📚 Roadmap Structure
📺 Roadmap Learning Guide
Who is this course right for?
Job seekers and students preparing for careers in the IT field
A backend developer who encountered a slow query in a live service but is at a complete loss as to where to begin troubleshooting.
A developer who is comfortable with feature development using SQL, but lacks confidence when faced with performance issues.
Aspiring Database Administrator (DBA)
Need to know before starting?
Kim Young-han's Practical Database Fundamentals
Inflearn Verified
613,329
Learners
43,041
Reviews
9,134
Answers
5.0
Rating
27
Courses
Educator
Before: Technical Director at Woowa Bros, Kakao, SK Planet
Author: Java ORM Standard JPA Programming
My goal is to provide education so that you can become a truly practical and competent developer.
EO Interview Video
The Life of Korea's Top Developer Instructor Young-han Kim [Part 1]
The Life of Younghan Kim, Korea's Top Developer Instructor [Part 2]
Gaebalbadak - A Country Youth Becomes the King of Development
Q&A Commemorating Inflearn Reaching 200,000 Users for the First Time
Q&A Commemorating Inflearn Reaching 300,000 Users for the First Time
All
104 lectures ∙ (21hr 10min)
Course Materials:
All
31 reviews
5.0
31 reviews
Reviews 3
∙
Average Rating 4.7
5
When I was preparing for employment, I used to be amazed by how easy it was to understand Mr. Kim Young-han’s lectures. They also helped strengthen my determination to find a job and motivated me to work hard in my preparation. Now that I’m employed, I’ve reached the stage where I think not only about basic database design but also about performance optimization. Even as I continue gaining hands-on experience, I’m very happy and grateful to still be learning alongside Mr. Kim Young-han’s lectures. Studying while envisioning an actual production database seems to make the lectures even more helpful. Thank you so much, as always, for your excellent lectures.
It makes me truly proud and happy to see that you’ve been with us since your days preparing for employment and have now grown into an amazing developer who considers performance optimization in your professional work, Suhyeon Lee :) I sincerely support your journey as a developer, as you continue to grow without pause, and I hope you’ll keep achieving great things in the future.
Reviews 36
∙
Average Rating 4.8
Edited
5
Hello. I sincerely congratulate you, Kim Young-han, on completing your incredible 7-year journey! I have been taking your classes ever since my first one in January 2023, eagerly waiting for the notifications of new course releases to pop up. Looking back now at those late-night study sessions after work, rubbing my sleepy eyes to stay awake, I sometimes wonder how I managed to keep at it. It was grueling and a bit daunting, but it also filled me with immense pride and happiness. It has been a tremendous privilege and a source of great pride to have accompanied you to the very end of this monumental journey, one in which you poured your heart and soul into every meticulous detail. Once again, thank you from the bottom of my heart for tirelessly completing this remarkable roadmap over the past 7 years.
Mr. Jong-cheol Park, thank you so sincerely for being with me on this long journey since 2023 and for celebrating the final period with me. Thanks to people like you, I was able to find the strength to complete the roadmap. I will be sincerely rooting for you, wishing that the path you walk ahead is always filled with great achievements and happiness!!!
Reviews 30
∙
Average Rating 5.0
5
You explained MySQL so clearly! Thank you.
Thank you for listening so cleanly, widn45^^!
Reviews 121
∙
Average Rating 5.0
Reviews 16
∙
Average Rating 5.0
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