Lief Tech — Dev, Business & Finance Blog

Weekly Retrospective — July Week 2, 2026

As it's gotten easier to build services with AI, I've been watching so many of them come to life and fade away.

Weekly Retrospective — July Week 1, 2026

It's been a while since I wrote my retrospective — I usually write one every week.

The Duolingo Founder Story: Luis von Ahn, a Green Owl, and the Plan to Make Education Free

Luis von Ahn invented CAPTCHA, sold reCAPTCHA to Google, and won a MacArthur 'genius' grant — then walked away from all of it to solve a problem from his childhood in Guatemala: education that only the rich can afford. How a computer scientist who was obsessed with harnessing human attention built Duolingo into a public company with hundreds of millions of learners.

3D Gaussian Splatting vs Unreal Engine: Two Ways to Build a 3D World — and Where Each One Ships

3D Gaussian Splatting captures reality; Unreal Engine authors it. This is a practical comparison of how you actually build a scene with each pipeline, what the result looks and behaves like, and the real productions — from Polycam captures to LED-wall virtual production — where each one ships.

LLMs Inside Unreal Engine: The New Skills Game Developers Need in 2026

In 2026, wiring a large language model into an Unreal Engine NPC stopped being a research demo and became a plugin you install from FAB. NVIDIA's ACE Game Agent SDK, Convai's NeuroSync, on-device small language models — here's what actually changed, and the concrete skills a game developer needs to build a character that talks back.

The Midjourney Founder Story: David Holz, the Company That Took No VC Money, and the $500M Bootstrap

David Holz spent nearly a decade building Leap Motion, raised $94M, and watched it sell for a fraction of its peak. Then he did the opposite: he started Midjourney with no outside capital, ~40 people, and a Discord bot — and turned it into a reported $500M-ARR business. How a burned VC skeptic built one of the most profitable companies in AI.

Living With Claude Fable 5: How the Most Capable Model Changes the Way You Actually Work

The Claude Fable 5 release notes tell you the parameters that changed. They don't tell you how it reshapes your day-to-day workflow — the timeouts, the prompts you have to unlearn, and why 'high' effort is usually the right default. A practitioner's field notes after a few weeks of building on Fable 5.

Luma's Bet: From Video Generator to a Single Model That Thinks in Pixels

Luma AI started as a 3D-capture app, became a top-tier AI video model with Ray3, and is now wagering its future on Uni-1 — a single 'unified intelligence' model that reasons in language and renders in pixels in one pass. Here's what Luma actually shipped, why the $4B valuation, and where it's heading.

The Figma Founder Story: Drones, a Meme Generator, and the $20 Billion Deal That Got Blocked

Dylan Field dropped out of college on a $100k Thiel grant, then spent four years building nothing anyone could see — burning through ideas like drones and a meme generator before landing on 'Google Docs for design.' How Figma survived a near-failure stealth period, a blocked $20B Adobe acquisition, and IPO'd in 2025 at $68 billion.

Weekly Retrospective — June Week 4, 2026

I spent a hectic month—three services, a review, a competition application, and more.

The Spotify Founder Story: How Daniel Ek Beat Free Music by Being Faster Than Theft

When Daniel Ek started Spotify, the music industry was being hollowed out by piracy and everyone agreed the answer was lawsuits. Ek disagreed. He bet that you could not sue people away from free music — you could only out-experience it. The story of how a working-class kid from a Stockholm suburb made streaming start in 200 milliseconds, survived years of brutal licensing fights, and turned 'better than stealing' into a $30-billion company.

The Best AI Video Models in 2026: Types, Differences, and Where This Is All Going

Veo 3.1, Kling 3.0, Runway Gen-4.5, Seedance, and the strange case of Sora's shutdown. A clear-eyed map of the AI video generation models that actually matter in 2026 — how they differ, which one to pick for what, and where the field is heading.

Claude Fable 5 and Mythos 5: What the New Models Change, and How They Perform

Anthropic's Claude Fable 5 is now its most capable widely released model, and Claude Mythos 5 brings the same engine to Project Glasswing. Here's what actually changed in the API, why thinking is now always on, and what the performance gains look like in practice.

The Stripe Founder Story: Two Brothers From Limerick and Seven Lines of Code

Stripe is now one of the most valuable private companies on earth, processing payments for millions of businesses. But it started with two teenage brothers from rural Ireland who had already sold one company before they could legally drink — and who were annoyed that taking money online was absurdly hard. Here's how Patrick and John Collison built it.

The Replit Founder Story: From a Browser Hack in Amman to a Billion-Dollar IDE

Replit lets anyone write and run code in a browser, and is now valued north of a billion dollars. But it started as an open-source side project by a kid in Amman, Jordan, who refused to believe that programming had to be hard to start. Here's how Amjad Masad turned a browser hack into a company betting on the next billion software creators.

Elon Musk's X Money Says It Will Pay You 6% on Savings. Is It Too Good to Be True?

X Money, the fintech app built inside X, is reportedly offering 6% APY on savings plus 3% cash back — roughly 15x the US national average savings rate. Here's how the offer works, where the 6% really comes from, and the catches worth understanding before you move your cash.

The Nvidia Founder Story: A Denny's Booth, a Sega Bailout, and 30 Days From Death

Nvidia is now one of the most valuable companies on earth and the engine room of the entire AI boom. But it began in a Denny's booth in 1993, nearly died after its first chip flopped, and survived only because the founder told a customer the truth and a Japanese games company paid him anyway. Here's how Jensen Huang built it.

Anthropic Shipped Its Most Powerful Claude Yet — Then the US Government Pulled the Plug

On June 9, 2026, Anthropic released Fable 5 and Mythos 5, its most capable models ever. Three days later it suspended access after a US export-control directive limited the models to US nationals. Here's what happened, why national security got involved, and what it means for the AI industry.

Weekly Retrospective — June Week 3, 2026

It feels like I've just been frantically tackling one thing after another, and somehow it's already the end of June.

When You Should NOT Use Sub-Agents

Sub-agents are the default reflex for any hard task now — but Anthropic's own engineering guidance is blunt about where they backfire. A look at the token math, the decomposition test, and the failure modes that mean a single agent is the right call.

The Notion Founder Story: Noodles, Kyoto, and a Rewrite That Saved the Company

Notion is a $10B+ workspace used by over 100 million people — but in 2015 it was two founders in a cheap Kyoto apartment who had scrapped their code, laid off their only employees, and were borrowing money from mom. Here's how Ivan Zhao and Simon Last almost died, then rebuilt.

From Agent Engineering to Harness Engineering to Loop Engineering

The discipline of building with LLMs has shifted three times in two years — from crafting agents, to crafting the harness around them, to crafting the loop the agent runs inside. Here's what each shift actually changed and why it matters.

Commercial Real Estate Investing: The Complete Guide

A practical, numbers-first walkthrough of investing in commercial retail property — how yield really works, the location and tenant signals that matter, the due diligence that protects your downside, and the taxes and exit math most first-time buyers get wrong.

How to Research Your App's Target Audience (With Real Examples)

A practical method for identifying and validating your app's real target audience — using App Store reviews, community listening, competitor changelogs, and micro-experiments, with examples from Notion, Calm, and Duolingo.

Why Developers Leave Claude for Open-Source Models

Cost, privacy, refusals, and a narrowing capability gap are pushing developers from Claude's API to self-hosted open-source models. Here's what that shift looks like from the inside.

From Side Project to Acquisition: The Moltbook Story

A first-person account of building Moltbook — a developer knowledge-capture tool — from a weekend prototype to a successful acquisition, and what the journey taught me about shipping with intent.

MCP, Skills, Hooks, Sub-agents: What They Are and How to Choose

Claude Code offers four extension layers — MCP, skills, hooks, and sub-agents — that look similar but operate at fundamentally different depths. Here's a clear framework for choosing the right one.

Back to Basics: LLM, RAG, and GraphRAG

A clear-eyed look at what large language models, retrieval-augmented generation, and graph-based RAG actually are — and when each one earns its place.

My personal CLI-replacement tool for running multiple MVPs solo—should I open-source it?

A CLI-replacement tool I built to run and manage multiple solo projects—shared standards, per-project issue tracking, and accumulated Git history/context, all in one place.

Kubernetes vs AWS Lambda: When Serverless Actually Saves You Money

A clear-eyed look at the real cost math behind Kubernetes and AWS Lambda — and how to know which one is bleeding your budget without you noticing.

Google Colab CLI: Notebooks Finally Meet the Terminal

Google's Colab CLI lets developers manage notebooks and runtimes from the command line, making Colab viable in CI pipelines and automated workflows for the first time.

Samsung vs SK Hynix: the HBM battle that will decide Korea's AI chip future

Samsung Electronics is fighting to reclaim its position in high-bandwidth memory as AI data centers reshape the semiconductor market. Here's what's actually at stake.

Ray-Ban Meta vs. Oakley Meta AI Glasses: Features, Differences, and How to Try Them In-Store

A practical guide to Ray-Ban Meta and Oakley Meta AI glasses — what they do, how they differ, where to try them on at an offline store, and which one is right for you.

The Future of the XR Industry: Where AR, VR, and AI Converge

A grounded look at where the XR industry is heading — key players, AI-powered glasses replacing phones, spatial OS adoption, real challenges, and a realistic 3–5 year outlook.

What's New in Apple Intelligence: The 2026 Update Guide

A practical overview of Apple Intelligence in 2026 — which devices support it, what features have landed, how it compares to the 2024 launch, and how everyday users actually benefit.

SDKs and Developer Skills for AI Glasses Content Creation

A practical guide for developers and content creators on which SDKs, APIs, and skills to learn when building apps or content for AI smart glasses like Ray-Ban Meta and Oakley Meta.

US-Iran Ceasefire Talks and the Fuel Surcharge Effect

How US-Iran peace negotiations affect oil prices — and what that means for fuel surcharges in shipping and logistics.

Neural 3D Rendering: NeRF, Gaussian Splatting, and the Tools That Power Them

A technical deep-dive into neural 3D rendering — how NeRF and Gaussian Splatting work under the hood, how they are trained, and a survey of commercial services and open-source tools available today.

Weekly Retrospective — June Week 2, 2026

AR/VR/XR Device Landscape: 2026 Overview

A concise reference covering commercially available AR, VR, and XR headsets in mid-2026 — key specs, use cases, and notable differences.

The end of jeonse and what it means for renters in Korea

Korea's unique deposit-based rental system is shrinking. Understanding why — and what's replacing it — matters for anyone renting or buying in the current market.

TSMC and the AI chip bottleneck Wall Street can't price correctly

Every AI company needs TSMC. Only one TSMC exists. Understanding that dependency is the starting point for understanding almost any AI hardware investment.

ISA: the Korean tax-free savings account most people don't use

If you're investing in Korea without an ISA, you're paying taxes you don't have to. Here's what the account does and why it's worth ten minutes of setup.

Seoul's apartment shortage and why reconstruction takes so long to fix it

Seoul has been trying to solve its housing supply problem for decades. Here's why each solution takes longer than the problem it's trying to address.

Korea's new mortgage rule: why landlords can't roll over their loans anymore

The Nvidia market worth watching now isn't data centers — it's robots

What to Check During a Property Visit: Real Info That Photos Don't Show

Why Did the Space Sector Suddenly Collapse? June's Selloff Explained

This Summer's Heat Wave: Key Points of the 2026 Vulnerable Population Protection Plan

What should I need to do as an IT Company owner

Majoring in AI or Software? Don't Miss the New AI Academic Incentive Student Loan

600M KRW Mortgage Cap: In 2026, Real Estate Comes Down to Loans

Big Tech's Data Center Spending This Year Is Not 725 Trillion Won — It's Dollar-Scale

Today's Financial Benefit: 2026 Small Business Stability Voucher (Up to 250,000 KRW)

Where Are Home Prices Now? Mid-2026 Korean Real Estate Check-In

Google Unveils Gemini Omni — A Turning Point in AI Video Generation

Weekly Retrospective — June Week 1, 2026

Why do some people always lack money, while others become richer?, The money-making wisdom of the Babylonian rich

My Experience Using All 7 Major Korean Blogging Platforms

The Money Book, How to Create a Money System

Key lessons learned from Seino’s teachings

Weekly Retrospective — May Week 5, 2026

Complete Office Contract Checklist — 15 Things You Must Check Before Stamping

Register your business, don’t delay, invest just 30 minutes

Is an agreement to end the US-Iran war imminent? 60-day ceasefire MOU

Secondary battery market in 2026, where is it now?

Migrating from Permanent Access Tokens to Token Exchange — Why Order Matters

Why the 2026 US midterm elections are important for Crypto

SpaceX, space technology, U.S.-related stocks and domestic stocks

SpaceX IPO listing news and Starship V3 12th test flight success

Weekly Retrospective — May Week 2, 2026

Weekly Retrospective — May Week 1, 2026

Weekly Retrospective — April Week 4, 2026

Weekly Retrospective — April Week 1, 2026

Startup & Product Glossary: Terms Every Solo Founder Should Know

Context Management — How I Do It Now

Claude Code Routines vs Cowork Schedule — What's the Difference?

Create a PM task automation agent with local LLM + Claude Code

Flutter review

Deepening Flutter asynchronous tasks

Dart basic grammar

DVA-C02 Preparation Material 5 - Event Handling & Data Streaming

DVA-C02 Preparation Material 4 - Network & CICD

DVA-C02 Preparation Material 3 - Security & Logging & Monitoring

DVA-C02 Preparation Material 2 - Storage

DVA-C02 Preparation Material 1 - Server & Serverless

Part 13. Learn about AWS - Security, ETC at once

Part 12. AWS at a glance - SAM, CDK, Cognito, Other Serverless Services

Part 11. AWS at a glance - API Gateway, CICD

Part 10. AWS at a glance - DynamoDB

Part 9. AWS - Lambda at a glance

Part 8. AWS at a glance - CloudWatch, CloudTrail

Part 7. Learn about AWS at once - SQS, SNS, Kinesis

Part 6. AWS at a glance - Elastic Beanstalk, CloudFormation

Part 5. Learn about AWS at once - ECS, ECR, Copilot, EKS

Part 4. AWS at a glance - S3, CloudFront

Part 3. Learn about AWS at once - Route53, VPC

Part 2. Learn about AWS at once - ELB, ASG, RDS, Aurora, ElastiCache

Part 1. Learn about AWS at once - IAM, EC2, EC2 Instance Storage

Getting started with AWS, all at once

Transactional annotation

test double

Software Development Methodology

Understanding query tuning

About Python

Leetcode 100

Kotlin basic syntax compared to Java

Google DeepMind SynthID and the principles of digital watermarking

Git Command Cleanup

Reset GCP migration settings

Things to keep in mind when designing entities

DeadLock and Redis queues

Back-end developer interview preparation questions - Web

Back-end developer interview preparation questions - Java

Considerations when designing backend architecture

AWS Various Deployment Methods

Types of Architecture

Open University Department of Computer Science

Contribute to Spring Security open source

Spring Security in Action - Part 2. Implementation (Chapters 8-14)

Spring Security in Action - Part 2. Implementation (Chapters 3-7)

Spring Security in Action - Part 1. first step

Contribute to Spring Batch open source

Project

Spring Boot and JPA Practical Mastery Roadmap

Learn Kotlin by Example

Learn the basics of large-scale system design through virtual interview examples

Java multithreading, concurrency, and performance optimization

View all information processing engineer practical content and past exam materials at once

Data-driven application design

Concurrent programming by language

Love Lessons

[Today’s Coding] Step8. Backend - Redis Write-Through Caching processing

[Today’s Coding] Step7. Backend - Implementation of table creation and search functions using JPA

[Today’s Coding] Step6. Backend - Apply Swagger and modify ERD

[Today’s Coding] Step5. Frontend - Creating a main page carousel

[Today’s Coding] Step4. Frontend - Setting up Thymeleaf Layout

Recommended free life/plan management tools

[Algorithm] Concepts of DFS and BFS and Java implementation

Design Your Language

[MySQL] Wanted Backend Onboarding Challenge February class content review

[Today’s Coding] Step3. Backend - database connection

IT Trends 2023

[Today’s Coding] Step2. Planning - project design and conception

Manage Your Mood, Manage Your Life

[MSSQL] TRANSACTION ISOLATION LEVEL

[Information processing engineer writing] Software development

[Information processing engineer handwriting] Software design

[Information processing article writing] Utilization of programming language

[Information processing article notes] Database construction

[Information processing engineer handwriting] Information system construction and management

[Today’s Coding] Step 1. Start of the project

[IT 5-Minute Dictionary] Assignment #13

[IT 5-Minute Dictionary] Assignment #10

[IT 5-Minute Dictionary] Assignment #06

[Redis] About Redis - terminology, DB differences, data types, installation, and Spring Boot connection

[IT 5-Minute Dictionary] Assignment #05

[IT 5-Minute Dictionary] Assignment #02

[2022 Reading Review] Nothing will change if you cry

[2022 Reading Review] The Rich Man’s Bowl

[2022 Reading Review] Psychology for Lazy Perfectionists

[Information Processing Technician] Final review of exam scope

[Information Processing Technician Practical] Key Contents of the 2nd Session in 2021 (1)

[Information Processing Technician Practical] Key Contents of the 3rd Session in 2021 (2)

[Information Processing Technician Practical] 3rd session in 2021 Key content (1)

[Pragmatic Programmer] Chapter 7. While coding

[The Art of Scalability] Book Review

[Pragmatic Programmer] Chapter 4. pragmatic paranoia

[Pragmatic Programmer] Chapter 3. basic tools

[Reservation Program] Extra 3. Apply SSL with Cafe24 Web Hosting SecureSign

[Reservation Program] Extra 2. Errors that occurred during the use and distribution of Cafe24 Tomcat JSP hosting

[Reservation Program] Extra. Current hosting using cloud computing and selection of domestic hosting company

[Reservation Program] Step2. Create an AWS RDS database

[Reservation Program] Step1. Complete overview of creating a project

[Reservation program] Solving issues that arose while creating

[Reservation Program] Development Intention and Requirements

[SQLD] 1. SQL basics

[SQLD] 2. Data model and performance

[SQLD] 3. Understanding data modeling

Blockchain and its pros and cons

[Spring] Spring MVC Package Explorer configuration

[Spring] Features of Spring framework

[2021 Reading Review] Happy Programming

CS basics summarized with a backend roadmap [1-1] Internet

[Information processing engineer practice] Interface exception handling, supertype and subtype, data flow diagram, normalization, semi-normalization, partition, code, middleware

[Information processing technician practice] SW development security, object-oriented programming, types of programming languages, cloud computer, interaction

Creating ALB with modified GUI

[2021 AWSome Day] Summary of lecture contents

Creating dynamic web pages using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Resolving issues in 10 steps

[Github] Considerations and Markdown when writing ReadMe

[Extension Program] 03. A useful tip for those who are new to extension program development!

[Extension program] 02. Project function design

[Extension Program] 01. Project Design

[Python] Important standard library_itertools

[Python] About crawling

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Applying Https in 9 steps

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Step 0 Project Overview

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Connect to domain purchase in 8 steps

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Errors that occurred during 7-step deployment (steps 5 and 6)

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - 6-step deployment (2)

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - 5-step deployment (1)

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Step 4 XXS prevention, writing test code

Creating a dynamic web page using Spring intializr (Gradle), IntelliJ, and AWS EC2 - 3 steps Thymeleaf mail sending

Creating dynamic web pages using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Step 2 project configuration, Git integration

Creating a dynamic web page using Spring internalizr (Gradle), IntelliJ, and AWS EC2 - Step 1 Gradle project basic settings

Things you need to know to become a backend developer

[JavaScript] My Quick Reference for Core Basics

[HTML/CSS] My Quick Reference for Core Basics

[JDBC] DAO, DTO Concepts and DML Code Structure

Study method the day before writing an information processing article + memorization tips

[JDBC] Applying SQL statements in Eclipse (DML, DDL, DCL, TCL)

[Java] Arrays and Bubble Sort

[Java] Applied Random and Arrays

[Java] While, do-While, Math.random() and Random Class

[Java] Applied For Loop and Nested For Loops

[Java] For Loop with Examples

[Java] Wrapper, Math Classes, if and switch Statements

[Java] Scanner and Input Validation

[Java] Java installation and basic concepts

[Java] Constructor, Casting, and Operators

[Java] Data and Variables

Java Star Pattern Problems

18 [Instructor] Java Standards ch08

15 [Instructor] Java Essentials ch07

14 [Instructor] Java Standards ch07

11 [Instructor] Java Essentials ch06