ppp1969 · Jul 14, 2026 · Jul 14, 2026
diff --git a/Dockerfile b/Dockerfile
@@ -12,7 +12,7 @@ RUN chmod +x ./gradlew && ./gradlew --no-daemon clean bootJar -x test
 FROM eclipse-temurin:17-jre
 
 WORKDIR /app
-ENV JAVA_TOOL_OPTIONS="-Xmx384m -XX:MaxRAMPercentage=75"
+ENV JAVA_TOOL_OPTIONS="-Xms64m -Xmx256m -XX:+UseSerialGC -XX:ActiveProcessorCount=1 -XX:MaxMetaspaceSize=128m -XX:ReservedCodeCacheSize=64m -XX:MaxDirectMemorySize=32m -Xss256k -XX:+ExitOnOutOfMemoryError"
 COPY --from=build /app/build/libs/*.jar app.jar
 
 EXPOSE 8080

diff --git a/docs/RENDER_FREE_DEPLOYMENT_RUNBOOK.md b/docs/RENDER_FREE_DEPLOYMENT_RUNBOOK.md
@@ -78,7 +78,10 @@ spring:
 ```env
 DB_MAX_POOL_SIZE=2
 DB_MIN_IDLE=1
-JAVA_TOOL_OPTIONS=-Xmx384m -XX:MaxRAMPercentage=75
+JAVA_TOOL_OPTIONS=-Xms64m -Xmx256m -XX:+UseSerialGC -XX:ActiveProcessorCount=1 -XX:MaxMetaspaceSize=128m -XX:ReservedCodeCacheSize=64m -XX:MaxDirectMemorySize=32m -Xss256k -XX:+ExitOnOutOfMemoryError
+SPRING_MAIN_LAZY_INITIALIZATION=true
+SPRINGDOC_ENABLED=false
+HIBERNATE_DEFAULT_BATCH_FETCH_SIZE=100
 ```
 
 ## DB 이전
@@ -168,9 +171,12 @@ CHARACTER_IMAGE_QUALITY=medium
 CHARACTER_IMAGE_WIDTH=1024
 CHARACTER_IMAGE_HEIGHT=1024
 CHARACTER_IMAGE_COUNT=1
-JAVA_TOOL_OPTIONS=-Xmx384m -XX:MaxRAMPercentage=75
+JAVA_TOOL_OPTIONS=-Xms64m -Xmx256m -XX:+UseSerialGC -XX:ActiveProcessorCount=1 -XX:MaxMetaspaceSize=128m -XX:ReservedCodeCacheSize=64m -XX:MaxDirectMemorySize=32m -Xss256k -XX:+ExitOnOutOfMemoryError
 DB_MAX_POOL_SIZE=2
 DB_MIN_IDLE=1
+SPRING_MAIN_LAZY_INITIALIZATION=true
+SPRINGDOC_ENABLED=false
+HIBERNATE_DEFAULT_BATCH_FETCH_SIZE=100
 ```
 
 Google OAuth를 Render 백엔드로 사용할 경우:

diff --git a/src/main/java/com/kw/readwith/config/AsyncConfig.java b/src/main/java/com/kw/readwith/config/AsyncConfig.java
@@ -25,17 +25,17 @@ public class AsyncConfig implements AsyncConfigurer {
     public Executor imageGenerationExecutor() {
         ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
 
-        // 코어 스레드: 동시에 2개의 이미지만 생성
-        executor.setCorePoolSize(2);
+        // Render Free 512MB 환경에서는 이미지 생성을 한 번에 하나만 실행한다.
+        executor.setCorePoolSize(1);
 
-        // 최대 스레드: 부하가 높을 때 최대 3개까지 허용
-        executor.setMaxPoolSize(3);
+        executor.setMaxPoolSize(1);
 
-        // 대기 큐: 50개까지 대기 가능
-        executor.setQueueCapacity(50);
+        executor.setQueueCapacity(10);
 
         // 스레드 이름 prefix (로그 추적 용이)
         executor.setThreadNamePrefix("image-gen-");
+        executor.setAllowCoreThreadTimeOut(true);
+        executor.setKeepAliveSeconds(60);
 
         // 큐가 가득 찰 경우 호출한 스레드에서 직접 실행
         executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
@@ -50,9 +50,11 @@ public Executor imageGenerationExecutor() {
     public Executor normalizationJobExecutor() {
         ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
         executor.setCorePoolSize(1);
-        executor.setMaxPoolSize(2);
-        executor.setQueueCapacity(20);
+        executor.setMaxPoolSize(1);
+        executor.setQueueCapacity(5);
         executor.setThreadNamePrefix("normalization-job-");
+        executor.setAllowCoreThreadTimeOut(true);
+        executor.setKeepAliveSeconds(60);
         executor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
         executor.initialize();
         return executor;

diff --git a/src/main/java/com/kw/readwith/service/CharacterImageService.java b/src/main/java/com/kw/readwith/service/CharacterImageService.java
@@ -206,8 +206,8 @@ public GeneratedCharacterImage generateTextImage(Character character) throws IOE
     }
 
     public String uploadGeneratedImage(Character character, byte[] imageData, String s3KeyName) {
-        String base64Image = Base64.getEncoder().encodeToString(imageData);
-        return s3Manager.uploadFileFromBase64(s3KeyName, base64Image, "image/png");
+        s3Manager.uploadBytes(s3KeyName, imageData, "image/png");
+        return s3Manager.getObjectUrl(s3KeyName);
     }
 
     public String buildReferenceCandidateS3KeyName(Character character, Long assetId) {

diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
@@ -2,6 +2,8 @@ server:
   port: ${PORT:8080}
 
 spring:
+  main:
+    lazy-initialization: ${SPRING_MAIN_LAZY_INITIALIZATION:true}
   datasource:
     url: ${DATABASE_URL:jdbc:mysql://${AWS_DB_URL}:3306/readwith_db?serverTimezone=Asia/Seoul&characterEncoding=UTF-8&useSSL=true&requireSSL=true}
     username: ${DATABASE_USERNAME:${AWS_DB_USERNAME}}
@@ -30,7 +32,7 @@ spring:
         use_sql_comments: true
         hbm2ddl:
           auto: validate
-        default_batch_fetch_size: 1000
+        default_batch_fetch_size: ${HIBERNATE_DEFAULT_BATCH_FETCH_SIZE:100}
         # 배치 INSERT 최적화 (성능 개선)
         jdbc:
           batch_size: 50
@@ -69,6 +71,12 @@ spring:
           quality: ${CHARACTER_IMAGE_QUALITY:medium}
           n: ${CHARACTER_IMAGE_COUNT:1}
 
+springdoc:
+  api-docs:
+    enabled: ${SPRINGDOC_ENABLED:false}
+  swagger-ui:
+    enabled: ${SPRINGDOC_ENABLED:false}
+
 epub:
   normalization:
     enabled: ${EPUB_NORMALIZATION_ENABLED:true}

diff --git a/src/test/java/com/kw/readwith/service/CharacterImageServiceTest.java b/src/test/java/com/kw/readwith/service/CharacterImageServiceTest.java
@@ -161,7 +161,7 @@ void generateAndSaveImage_succeeds() throws Exception {
         Files.write(tempImage, new byte[]{1, 2, 3, 4});
 
         when(characterRepository.findByIdWithBook(testCharacter.getId())).thenReturn(Optional.of(testCharacter));
-        when(s3Manager.uploadFileFromBase64(anyString(), anyString(), eq("image/png")))
+        when(s3Manager.getObjectUrl("character-images/1/10.png"))
                 .thenReturn("https://cdn.readwith.store/character-images/1/10.png");
 
         ImageResponse imageResponse = mock(ImageResponse.class);
@@ -183,7 +183,7 @@ void generateAndSaveImage_succeeds() throws Exception {
         assertThat(imageOptions.getWidth()).isEqualTo(1024);
         assertThat(imageOptions.getHeight()).isEqualTo(1024);
         assertThat(imageOptions.getN()).isEqualTo(1);
-        verify(s3Manager).uploadFileFromBase64(eq("character-images/1/10.png"), anyString(), eq("image/png"));
+        verify(s3Manager).uploadBytes(eq("character-images/1/10.png"), any(byte[].class), eq("image/png"));
         verify(transactionService).updateImageAndStatus(
                 testCharacter.getId(),
                 "https://cdn.readwith.store/character-images/1/10.png",
@@ -197,7 +197,7 @@ void generateAndSaveImage_uploadsBase64JsonResponse() {
         byte[] generatedImage = new byte[]{9, 8, 7, 6};
 
         when(characterRepository.findByIdWithBook(testCharacter.getId())).thenReturn(Optional.of(testCharacter));
-        when(s3Manager.uploadFileFromBase64(anyString(), anyString(), eq("image/png")))
+        when(s3Manager.getObjectUrl("character-images/1/10.png"))
                 .thenReturn("https://cdn.readwith.store/character-images/1/10.png");
 
         ImageResponse imageResponse = mock(ImageResponse.class);
@@ -210,13 +210,13 @@ void generateAndSaveImage_uploadsBase64JsonResponse() {
 
         characterImageService.generateAndSaveImage(testCharacter.getId());
 
-        ArgumentCaptor<String> base64Captor = ArgumentCaptor.forClass(String.class);
-        verify(s3Manager).uploadFileFromBase64(
+        ArgumentCaptor<byte[]> imageCaptor = ArgumentCaptor.forClass(byte[].class);
+        verify(s3Manager).uploadBytes(
                 eq("character-images/1/10.png"),
-                base64Captor.capture(),
+                imageCaptor.capture(),
                 eq("image/png")
         );
-        assertThat(Base64.getDecoder().decode(base64Captor.getValue())).containsExactly(generatedImage);
+        assertThat(imageCaptor.getValue()).containsExactly(generatedImage);
         verify(transactionService).updateImageAndStatus(
                 testCharacter.getId(),
                 "https://cdn.readwith.store/character-images/1/10.png",