Faith & Code | Reflections by Errong

Only God Gives Certainty We live in an age overflowing with information but starving for certainty. Every day we are surrounded by countless opinions through social media, news outlets, podcasts, and online discussions. Everyone seems to have a perspective, yet very few are willing to say, "This is true." As Christians, we are not immune to this cultural shift. Even Bible studies can slowly become discussions about what each person thinks instead of seeking what God has already spoken. This sermon on Proverbs 3:5-6 challenged me to ask a simple but profound question: Where does my certainty come from? Trust Is More Than Agreement When Proverbs tells us to "Trust in the Lord with all your heart," it is not simply asking us to agree with God's existence. Biblical trust means placing the full weight of our lives upon Him. It is like the person trapped in a burning building who jumps into the firefighters' rescue net. There is complete dependence. Ther...

  Looking Ahead with Confidence: Christ Has Already Won "Lead us not into temptation, but deliver us from the evil one." — Matthew 6:13 Celebrating fifty years as a church is more than commemorating a milestone. It is celebrating fifty years of God's unwavering faithfulness to His bride. While anniversaries naturally invite us to look back with gratitude, this sermon challenged us to do something equally important—to look ahead with confidence. As Christians living in Canada, it is easy to feel concerned about the future. Biblical values are increasingly unpopular, churches face growing cultural pressure, and many parents and grandparents worry about the spiritual future of their children. These concerns are real, but they are not the whole story. The Heidelberg Catechism reminds us that every Christian lives in the middle of a spiritual war. The Battle We Often Forget When we hear the words, "Lead us not into temptation," we often think about avoiding bad habit...

The Church's Greatest Challenge: Remaining Faithful to the Truth Celebrating fifty years of a local church is a wonderful milestone. Over five decades, countless lives have been touched through baptisms, weddings, funerals, professions of faith, missionary work, and faithful worship. Behind every ministry, every answered prayer, and every transformed life stands one unchanging reality—God's faithfulness. As we look back with gratitude, we should also look forward with wisdom. Buildings may age, leadership may change, cultures may shift, but one challenge remains constant for every generation of Christians: Will we remain faithful to the truth of God's Word? The Church Does Not Belong to Us It is tempting during anniversary celebrations to focus on human accomplishments. We thank faithful pastors, elders, deacons, volunteers, and members. Their service certainly deserves appreciation. Yet Scripture reminds us that Christ is the One who builds His church. Ev...

ParallelStream vs Virtual Threads in Java 21: What Actually Works for Database Workloads Java offers multiple ways to parallelize work, but not all concurrency models are suitable for database-heavy workloads. In modern systems, especially with large batch processing (e.g., 10,000–50,000 IDs), choosing the right model can drastically change performance. This article compares ParallelStream and Virtual Threads (Java 21) using a real-world scenario: batch database queries in Oracle. 🧠 The Problem: Large Batch Database Queries A common backend scenario is fetching data using large ID lists: Example: - 40,000 transaction IDs - Chunked into 1,000 per query - ~40 database queries executed The key question becomes: how do we execute these 40 queries efficiently? ⚙️ Approach 1: ParallelStream IntStream.range(0, batchCount) .parallel() .mapToObj(i -> repository.query(batch)) How it works Uses ForkJoin common pool Thread count ≈ number of CP...

How to Optimize a Slow JPA Query Processing 40K+ IDs (Real Performance Tuning Guide) Handling large datasets efficiently is one of the most common challenges in backend engineering. In this post, I’ll walk through how a query processing 40,000+ IDs went from ~24 seconds down to a few seconds using practical optimization techniques. All domain-specific details have been intentionally removed to focus purely on reusable engineering patterns. 📉 The Problem A service fetches data using a JPA query with a large IN clause and joins between tables: SELECT new SomeDto( A.primaryId, A.field1, A.field2, B.field3, C.metric1, C.metric2 ) FROM EntityA A LEFT JOIN A.relatedEntity B LEFT JOIN EntityC C ON C.refId = A.primaryId WHERE A.primaryId IN :ids Even with chunking (~900 IDs per query), total execution time was around 24 seconds . 🚨 Root Causes Unoptimized JOIN conditions Missing database indexes Sequential query execution ORM (JPA) over...

How We Optimized a Spring Boot Pagination Query by 36× (From 1.8 Minutes to 3 Seconds) In high-traffic backend systems, slow database queries are often the hidden bottleneck that quietly kills performance. In our case, a paginated query powering a reporting API was taking 1.8 minutes to respond under load. After optimization, we reduced it to ~3 seconds . 36× faster ~97.2% less execution time ~3500% performance improvement Here’s how we did it — and the key lessons you can apply immediately. 🧱 The Problem: Slow Pagination Query We had a Spring Data JPA query backing a paginated API. It involved multiple filters, joins, and was returning a large dataset. Original issues: Full entity loading Heavy object graph hydration Unnecessary columns fetched Inefficient filtering logic Expensive pagination count The database schema (simplified and anonymized) looked like this: TABLE txn_line ( line_id BIGINT, order_id BIGINT, product_code ...

Sprint Design Notes: LDAP (OUD vs AD) and SQL Lookup Optimization Today was a light but productive design session focused on aligning the team on upcoming sprint stories. While the implementation itself is not overly complex, the discussion surfaced two important architectural considerations: How we handle large identifier lookups in SQL queries How we manage LDAP-based authentication and group access control (OUD vs AD) This post documents both topics for future reference and knowledge sharing. SQL Lookup Design: Handling Large Identifier Lists One of the stories requires supporting lookup by identifier list, where the input may contain a comma-separated list of values. The Problem Directly passing a large list of identifiers into SQL introduces several risks: SQL query length limitations (database dependent) Overly large IN (...) clauses Performance degradation on large parameter sets SELECT * FROM orders WHERE identifier IN (...very long list...

  Three More Real-World Auto-Fill Bugs We Found While Building a Chrome Extension Yesterday we fixed an issue where our auto-fill engine was targeting invisible input elements instead of the actual visible fields. After deploying that fix, we continued testing across multiple vendor websites and discovered three additional issues. None of them were particularly complicated, but all three caused auto-fill failures in real-world scenarios. This is a good reminder that browser automation is often less about complex algorithms and more about handling the countless variations of web forms. Background We are building a Chrome extension that automatically fills customer information such as: First Name Last Name Email Address Phone Number Address Province Postal Code The extension works across multiple vendor websites, each built with different technologies and UI frameworks. During testing, we discovered the following issues. Issue #1: document.querySelector Only Returns the First Match I...

Extension auto-fill works on most vendor sites, but fails on Angular-based page (ng-pristine vs ng-dirty issue) Problem Background We are building a browser extension that auto-fills customer information (first name, last name, email, phone number, address, etc.) into different vendor websites. Each vendor site has different page structures, and our content script is responsible for detecting input fields and filling data automatically. Issue Symptom Most vendor sites work correctly. However, on one specific vendor site, auto-fill does not work: Our logs show values are being filled No visible changes appear in the UI Input fields remain empty from user perspective Filling input: firstName = John Filling input: email = test@example.com But UI still shows no updated values. Environment Extension: Chrome Extension (content script) Language: JavaScript Target site: Vendor web application Framework (discovered later): Angular Debugging Process W...

The Boldness of the Gospel in Acts 4 A personal reflection on the message of Peter and John before the religious leaders, the healing at the Temple gate, and the unstoppable advance of the Gospel. Introduction: When the Gospel Disrupts the World The message in Acts 4 captures a moment of intense tension: a miraculous healing has just taken place, and the public response is growing rapidly. A once-lame man is now walking, leaping, and praising God. But instead of joy alone, the event triggers opposition, confusion, and confrontation. What stands out is not only the miracle itself, but the “fallout” it produces—spiritual, social, and political. The Gospel of Jesus Christ does not remain private or neutral; it enters public space and forces a response. The Miracle and Its Meaning The healing at the Beautiful Gate is more than compassion—it is a visible sign that the risen Christ is alive...

Walking the Path of Faith On Sunday morning, I listened to a sermon based on Colossians 2:6-8. The message was especially meaningful because it was preached during a profession of faith and baptism service. While the sermon was directed toward those publicly declaring their faith, I found that its lessons apply to every Christian, regardless of age or how long they have followed Christ. The central theme was simple yet profound: the Christian life is a journey that begins by receiving Christ and continues by remaining in Christ. The Beginning of the Journey One illustration from the sermon stood out to me. The preacher compared the Christian life to a hiking trail. Before you can enjoy the journey, you must first start at the correct trailhead. If you begin on the wrong path, it does not matter how enthusiastically you walk—you will end up in the wrong destination. That is true spiritually as well. Many people believe Christianity is primarily about being a good person, foll...

Forgive Us Our Debts This week I listened to a sermon on the fifth petition of the Lord's Prayer: "And forgive us our debts, as we also have forgiven our debtors." (Matthew 6:12) One thought stayed with me long after the service ended: this is a remarkably bold prayer. When I pray these words, I am asking God to forgive a debt that I could never repay. Not reduce it. Not delay it. Not give me more time. Forgive it completely. I think many of us underestimate how serious our sin is before a holy God. We often compare ourselves to other people and conclude that we are doing reasonably well. Yet Jesus tells a different story. In the parable of the unforgiving servant, He describes a debt so large that repayment is impossible. That is what our sin debt looks like before God. And yet He invites us to ask for forgiveness. That is what amazes me. God is perfectly just. He does not ignore sin or pretend it does not matter. Every wrong will be accounted for. Ever...

The Sixth Commandment: From Cain's Hatred to Christ's Love The Sixth Commandment, “You shall not murder” (Exodus 20:13), is often understood as a prohibition against physical killing. Yet Scripture reveals that God's concern goes much deeper than outward actions. In Genesis 4, the tragic story of Cain and Abel exposes the root of murder: a sinful heart filled with envy, anger, and hatred. This sermon explored Genesis 4 through the lens of the Sixth Commandment and showed both humanity's deep corruption and God's greater mercy in Jesus Christ. The story of Cain is not merely ancient history; it is a mirror held up to every human heart. The World Is Filled with Violence Because the Human Heart Is Corrupted Violence, murder, war, abortion, abuse, hatred, and division are not isolated problems. They are symptoms of a deeper disease. Since humanity's fall into sin, the world has become marked by conflict and death. Modern society often treats violence as no...

🧠 The Invisible System Behind Enterprise Browser Extensions (and Why Most Teams Get It Wrong) Most people think browser extensions are simple: “Build it → publish it → users get it.” In enterprise reality, it’s nothing like that. The moment you need: silent installation controlled rollout auto updates without IT tickets device targeting (not user guessing) …you accidentally end up building a distribution system disguised as an extension pipeline . ⚙️ The Architecture Nobody Sees At the center of everything is a simple idea: A browser extension is not “installed.” It is “subscribed to an update stream.” That stream is controlled by update.xml , and everything else is just delivery mechanics. 🏗️ High-Level Architecture Everything depends on one fragile but powerful contract: The update.xml URL must never change. Only its version and CRX pointer change. 📦 The Build Pipeline (Simple but Critical) We use a modern Web Extension b...