diff --git a/.gitignore b/.gitignore
index 549e00a..bf01670 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,33 +1,9 @@
-HELP.md
 target/
-!.mvn/wrapper/maven-wrapper.jar
-!**/src/main/**/target/
-!**/src/test/**/target/
-
-### STS ###
-.apt_generated
-.classpath
-.factorypath
-.project
-.settings
-.springBeans
-.sts4-cache
-
-### IntelliJ IDEA ###
-.idea
-*.iws
-*.iml
-*.ipr
-
-### NetBeans ###
-/nbproject/private/
-/nbbuild/
-/dist/
-/nbdist/
-/.nb-gradle/
-build/
-!**/src/main/**/build/
-!**/src/test/**/build/
-
-### VS Code ###
+.idea/
 .vscode/
+*.iml
+*.log
+.env
+.env.*
+!.env.example
+data/
diff --git a/.mvn/wrapper/maven-wrapper.properties b/.mvn/wrapper/maven-wrapper.properties
index 642d572..d853aaf 100644
--- a/.mvn/wrapper/maven-wrapper.properties
+++ b/.mvn/wrapper/maven-wrapper.properties
@@ -1,2 +1,2 @@
-distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.6.3/apache-maven-3.6.3-bin.zip
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.11/apache-maven-3.9.11-bin.zip
 wrapperUrl=https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar
diff --git a/pom.xml b/pom.xml
index 1f6c46d..751cff3 100644
--- a/pom.xml
+++ b/pom.xml
@@ -1,67 +1,74 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
+
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.3.4.RELEASE</version>
-        <relativePath/> <!-- lookup parent from repository -->
+        <version>3.5.16</version>
+        <relativePath/>
     </parent>
+
     <groupId>com.hoelee</groupId>
-    <artifactId>demo</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
-    <packaging>war</packaging>
-    <name>demo</name>
-    <description>Demo project for Spring Boot</description>
+    <artifactId>springboot-jsonplaceholder-demo</artifactId>
+    <version>1.0.0</version>
+    <name>springboot-jsonplaceholder-demo</name>
+    <description>A production-minded Spring Boot REST API showcase.</description>
 
     <properties>
-        <java.version>1.8</java.version>
+        <java.version>21</java.version>
     </properties>
 
     <dependencies>
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-thymeleaf</artifactId>
-        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-web</artifactId>
         </dependency>
-
         <dependency>
             <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-tomcat</artifactId>
-            <scope>provided</scope>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-validation</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-security</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-cache</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.github.ben-manes.caffeine</groupId>
+            <artifactId>caffeine</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-actuator</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-configuration-processor</artifactId>
+            <optional>true</optional>
         </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>
             <scope>test</scope>
-            <exclusions>
-                <exclusion>
-                    <groupId>org.junit.vintage</groupId>
-                    <artifactId>junit-vintage-engine</artifactId>
-                </exclusion>
-            </exclusions>
-        </dependency>
-
-        <!-- Additional add-on by Hoelee -->
-        <dependency>
-            <groupId>org.json</groupId>
-            <artifactId>json</artifactId>
-            <type>jar</type>
-            <version>20200518</version>
         </dependency>
         <dependency>
-            <groupId>com.squareup.okhttp3</groupId>
-            <artifactId>okhttp</artifactId>
-            <type>jar</type>
-        </dependency>
-        <dependency>
-            <groupId>org.thymeleaf</groupId>
-            <artifactId>thymeleaf</artifactId>
-            <type>jar</type>
+            <groupId>org.springframework.security</groupId>
+            <artifactId>spring-security-test</artifactId>
+            <scope>test</scope>
         </dependency>
     </dependencies>
 
@@ -73,5 +80,4 @@
             </plugin>
         </plugins>
     </build>
-
 </project>
diff --git a/src/main/java/com/hoelee/jsonplaceholder/ShowcaseApplication.java b/src/main/java/com/hoelee/jsonplaceholder/ShowcaseApplication.java
new file mode 100644
index 0000000..4cb75e9
--- /dev/null
+++ b/src/main/java/com/hoelee/jsonplaceholder/ShowcaseApplication.java
@@ -0,0 +1,23 @@
+package com.hoelee.jsonplaceholder;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
+import org.springframework.data.jpa.repository.config.EnableJpaAuditing;
+
+/**
+ * @version v1, 2024-10-21 08:05:00PM
+ * @author hoelee
+ * Learning note: configuration scanning and JPA auditing keep cross-cutting setup explicit and compact.
+ */
+@SpringBootApplication
+@ConfigurationPropertiesScan
+@EnableJpaAuditing
+public class ShowcaseApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(ShowcaseApplication.class, args);
+    }
+}
+
+//~ v1, 2024-10-21 08:05:00PM - Last edited by hoelee
diff --git a/src/main/java/com/hoelee/jsonplaceholder/config/ApiProperties.java b/src/main/java/com/hoelee/jsonplaceholder/config/ApiProperties.java
new file mode 100644
index 0000000..b7519ed
--- /dev/null
+++ b/src/main/java/com/hoelee/jsonplaceholder/config/ApiProperties.java
@@ -0,0 +1,23 @@
+package com.hoelee.jsonplaceholder.config;
+
+import jakarta.validation.constraints.Max;
+import jakarta.validation.constraints.Min;
+import jakarta.validation.constraints.NotBlank;
+import java.time.Duration;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.validation.annotation.Validated;
+
+/**
+ * @version v1, 2024-10-21 09:05:00PM
+ * @author hoelee
+ * Learning note: typed, validated properties make operational settings discoverable and fail fast.
+ */
+@Validated
+@ConfigurationProperties(prefix = "app.api")
+public record ApiProperties(
+        @NotBlank String jsonPlaceholderBaseUrl,
+        Duration requestTimeout,
+        @Min(1) @Max(100) int importLimit) {
+}
+
+//~ v1, 2024-10-21 09:05:00PM - Last edited by hoelee
diff --git a/src/main/java/com/hoelee/jsonplaceholder/config/SecurityProperties.java b/src/main/java/com/hoelee/jsonplaceholder/config/SecurityProperties.java
new file mode 100644
index 0000000..16a2503
--- /dev/null
+++ b/src/main/java/com/hoelee/jsonplaceholder/config/SecurityProperties.java
@@ -0,0 +1,19 @@
+package com.hoelee.jsonplaceholder.config;
+
+import jakarta.validation.constraints.NotBlank;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.validation.annotation.Validated;
+
+/**
+ * @version v1, 2024-10-21 10:05:00PM
+ * @author hoelee
+ * Learning note: credentials are externalized so a repository never needs a real environment secret.
+ */
+@Validated
+@ConfigurationProperties(prefix = "app.security")
+public record SecurityProperties(
+        @NotBlank String editorUsername,
+        @NotBlank String editorPassword) {
+}
+
+//~ v1, 2024-10-21 10:05:00PM - Last edited by hoelee
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
new file mode 100644
index 0000000..6bcd053
--- /dev/null
+++ b/src/main/resources/application.yml
@@ -0,0 +1,35 @@
+spring:
+  application:
+    name: jsonplaceholder-showcase
+  datasource:
+    url: jdbc:h2:mem:postshowcase;MODE=PostgreSQL;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
+    username: sa
+    password:
+  jpa:
+    open-in-view: false
+    hibernate:
+      ddl-auto: update
+  cache:
+    caffeine:
+      spec: maximumSize=500,expireAfterWrite=10m
+  mvc:
+    problemdetails:
+      enabled: true
+
+management:
+  endpoints:
+    web:
+      exposure:
+        include: health,info
+  endpoint:
+    health:
+      show-details: never
+
+app:
+  api:
+    json-placeholder-base-url: https://jsonplaceholder.typicode.com
+    request-timeout: 2s
+    import-limit: 20
+  security:
+    editor-username: ${APP_EDITOR_USERNAME:demo-editor}
+    editor-password: ${APP_EDITOR_PASSWORD:changeit}
diff --git a/src/test/resources/application.yml b/src/test/resources/application.yml
new file mode 100644
index 0000000..948d7f9
--- /dev/null
+++ b/src/test/resources/application.yml
@@ -0,0 +1,11 @@
+spring:
+  datasource:
+    url: jdbc:h2:mem:postshowcase-test;MODE=PostgreSQL;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
+  jpa:
+    hibernate:
+      ddl-auto: create-drop
+
+app:
+  security:
+    editor-username: test-editor
+    editor-password: test-password