I also want to prepare for an Android technical interview... Are there any good lectures?

I've heard a lot about architecture... How should I design in practice...?

Why do you put an Interface in only one implementation in the Repository?

I built an app with JetPack Compose. But recomposition and state management are difficult

I think the app is fine now. But I wonder if performance can be measured and quantitatively improved...?

👨‍💻 Instructor introduction

Hello, Experience in designing and developing 5 large-scale apps and SDKs myselfWith one,
Year 6 I'm Song Sang-yoon, an Android developer.

Those who haven't been able to resolve their thirst like above... I think these are people who didn't get any cool answers even when searching. When I was a junior, I had many similar concerns. To quench my thirst, Self-analyze and reprocess knowledge from official technical websites, conferences, columns, etc.And now I'm looking for an answer.

Currently doing practical work Design and maintain 5 large-scale apps and SDKsWe have done it, and we are continuing to share problems, solutions, and technologies that were difficult while creating them. Because I like sharing development ecosystem knowledge Over 6 tech sessions in total, including the Droid Knights presentation on June 17, '25was announced, Approximately 100 posts on personal and company blogsI wrote But this time One-timeIt's not a conference or tech session that ends with, Curriculum-basedI would like to share it with you by organically linking broader and deeper knowledge with

However, even so, I think there are people who think the following.

No... Are there any lectures from better developers? Do I have to listen to this?

That's right. If you look at the current development lecture ecosystem, it is also true that developers who are superior to me often give lectures and provide high-quality knowledge. However, if you don't have time or money, I think it can be a bit difficult to take all kinds of courses from these people. Therefore, I have designed a course to resolve this inconvenience, and you can get the following skills.

More than one deep topic, overall knowledgeI will tell you about (eg., Architecture, Compose, Coroutine, Benchmark)
of them Organic connectionsFocusing on, Android mind map in my headI would like to draw it for you.
But even so We don't just pursue the breadth of knowledge; the depth required for app optimizationPursuing until,
Performance improvements Quantitative measurements up to ms/µsI'll show you how to improve it.
My lectures like this need to set a direction Suitable for 1.5 to 3 year oldsIt is determined that it is, and Android development Navigation roleI'll do it for you.

When we first want to build an app, what matters most?

'Composite'? 'Coroutine'? Or the 'Repository Pattern'? , 'DI'? They're all wrong. The first factor to consider is how the company makes money,Profit model (hereafter, strategic planning)This is it. Without strategic planning, the company cannot survive, and in the end, we are unable to hire us as developers. Therefore, we need to be able to observe what the company's strategic planning is.

Isn't development ability the most important thing for developers?

That's right. However, in order to build high-quality code, that is, a structured architecture, and make good use of Coroutine and Compose required for this purpose, reasonable planning, which is a higher level, is necessary. Why would that be the case? This is because in order for a product to be developed, the required tasks (eg., planning, design...) must be carried out sequentially, and this determines the direction of development. Therefore, if you are a true developer, you need not only to do simple development, but also to participate and give opinions from the planning stage.

스크린샷 2025-06-24 오후 9.45.31.png

_{(Most companies nowadays can't rule out the traditional waterfall model at all, even if they work in a two-week scrum or agile manner.)}

Once a strategic plan has been decided, based on it App planning (hereinafter referred to as service planning)This goes in. Service planning is carried out with mockup tools such as ppt and figma that we are familiar with. Even at this time, developers are not standing still”Does app planning make sense?”,”What domain-level data will the app use?” You must be able to observe and suggest opinions.

Once service planning has been completed, the next step “design”et “Server API operations”This will proceed. As Android developers, we look at design proposals, Check if there is anything to be systematised and make suggestions to the designerI'm going to do it, and while looking at the server API Suggest interface changes to server developers to group data to be used in appsI'm going to do it. Why is this work needed? First of all, if you have a design system, the development speed will be very fast due to increased UI recyclability. Also, if you group the data to be used in the app, the reuse rate is very high with much less business logic code, and the maintainability of the app increases.

스크린샷 2025-06-25 오전 10.59.56.png

_{I often compare Repository to a butcher shop that sells meat ^^}

Now the next step “App development”In the step, we will create an app by working on UI and linking the server API. I will fluently tell you what the problems in the pure app area are encountered while creating this way, and how to design an architecture and use asynchronous libraries, and the following are skills that can be improved through my lectures.

📚 Course table of contents highlights

CHAPTER1. [Architecture] From the framework, structure to design of an app

Architecture, why the hell should we use it? Rather than simply dividing layers, the key is to separate responsibilities and create a structure that is flexible to change. We will discuss the essence of the UI/domain/data layer, focusing on structures that survive in practice.

CHAPTER2. [Jetpack Compose] Basic background knowledge for UI design

Before drawing a UI, you must first grasp the core concepts of Compose. We'll look at where to manage state and when to change it, how Compose's declarative UI mindset and recomposition work, and build basic physical strength before actual design.

CHAPTER3. [Jetpack Compose] Internal operating principles for UI optimization

Jetpack Compose, optimization starts with recomposition. Understanding internal rendering structures such as SlotTable, Composition, and Reuse can really improve performance. Find a structured view of performance from within Compose.

CHAPTER4. [Jetpack Compose] Practical implementation of optimized UI

Performance improvements, theory alone are not enough. LazyColumn's scroll bounce phenomenon and even a structure that prevents indiscriminate recomposition. Based on optimization issues encountered in actual apps, students learn by directly implementing UI patterns that can be applied in practice.

CHAPTER5. [Flow] Kotlin asynchronous flow processing understood by cold and hot streams

Flow, why is it difficult? That's because I missed the essence of flow. From concepts to differences and lifecycle management between Cold Flow and Hot Flow, we go beyond using simple APIs and delve into proper usage in the domain/data layer.

CHAPTER6. [Coroutine] Concurrency library provided by Kotlin

Coroutine isn't just an asynchronous tool. From the differences with Thread, Dispatcher, Exception Handling, and even the role of Builder, we will reorganize the core concurrency concepts provided by Kotlin Coroutine from a practical perspective.

CHAPTER7. [Coroutine] Domain & Data Layer implementation

No more abstract explanations. Learn directly in code how Coroutine and Flow are designed and used in the Domain and Data Layer of actual app architectures. It clearly points out the link between layer-specific responsibilities and concurrency flows.

CHAPTER8. [Benchmark] Improving performance with craftsmanship

It's not enough to say “slow.” Using quantitative measurement tools such as Benchmark, Perfetto, and Matrix, we quantify app performance in ms and even practice how to actually improve it. Practical optimization starts with measurements.

Are you overwhelmed preparing for the Android technical interview?

After all, the biggest reason to listen to lectures Get a job or move to a good companyIt's probably to do it. So I myself Technical interview with approximately 130 questionsWe have prepared it. (Will continue to be updated in the future) This list [Android Framework], [Third-party Library], [Compose], [Architecture], [Coroutine+Flow], [OS], [Data Structure], [Kotlin], [Network] It consists of, and in fact, I Questions drawn up while preparing and reviewing interviews with famous IT companiesThis is it. I also want to share the regret I felt after not being interviewed so many times, in the hope that you will experience it less. tooth A list of golden interview questionsI will only share it with those who have taken my course and left a review.

_{However, the name of a specific company is not listed.}

Is this course constantly being updated?

It's not a lecture that ends with a picture, Approximately 3 years of maintenance after the course launch dateI promise. We promise to boldly remove the Deprecated part and update the part where the API has changed drastically. Course updates will be posted on the LinkedIn wall, so if you would like to receive updates, please add a friend! ^^ (Go to Song Sang-yoon LinkedIn)

_{Course maintenance periods may vary due to the Android ecosystem, personal circumstances of developers, etc.}

The direction of the lecture?

Again, my course doesn't go deep into one topic. Rather, we select only the knowledge required for Android application development, focus on organically connecting them, and aim to be able to use them directly in practice. Therefore, I promise to play a navigation role for junior Android developers who have not yet grasped the directionI give it to you

We've prepared so that you can spend less time searching and lost alone and quickly learn only the knowledge you need. This course will be a compass that can be used directly in practice.

From design to performance measurement: Architecture × Compose × Coroutine

From design to performance measurement: Architecture × Compose × Coroutine