diff --git a/tomcat/src/main/java/nextstep/jwp/controller/AbstractController.java b/tomcat/src/main/java/nextstep/jwp/controller/AbstractController.java
index 94fbf34b85..8671455159 100644
--- a/tomcat/src/main/java/nextstep/jwp/controller/AbstractController.java
+++ b/tomcat/src/main/java/nextstep/jwp/controller/AbstractController.java
@@ -33,6 +33,7 @@ protected HttpResponse doPost(HttpRequest request) throws Exception {
     private HttpResponse defaultInternalServerErrorPage() throws URISyntaxException, IOException {
         final Path path = PathFinder.findPath("/500.html");
         final String responseBody = new String(Files.readAllBytes(path));
-        return new HttpResponse(HttpStatus.INTERNAL_SERVER_ERROR, responseBody, ContentType.HTML);
+
+        return new HttpResponse.Builder(HttpStatus.INTERNAL_SERVER_ERROR, responseBody, ContentType.HTML).build();
     }
 }
diff --git a/tomcat/src/main/java/nextstep/jwp/controller/FileController.java b/tomcat/src/main/java/nextstep/jwp/controller/FileController.java
index ae6175e433..e0458cfb3a 100644
--- a/tomcat/src/main/java/nextstep/jwp/controller/FileController.java
+++ b/tomcat/src/main/java/nextstep/jwp/controller/FileController.java
@@ -22,6 +22,6 @@ protected HttpResponse doGet(HttpRequest request) throws Exception {
         var responseBody = new String(Files.readAllBytes(path));
         ContentType contentType = ContentType.findContentType(extension);
 
-        return new HttpResponse(HttpStatus.OK, responseBody, contentType);
+        return new HttpResponse.Builder(HttpStatus.OK, responseBody, contentType).build();
     }
 }
diff --git a/tomcat/src/main/java/nextstep/jwp/controller/HelloController.java b/tomcat/src/main/java/nextstep/jwp/controller/HelloController.java
index ca50e0defd..d64973ab62 100644
--- a/tomcat/src/main/java/nextstep/jwp/controller/HelloController.java
+++ b/tomcat/src/main/java/nextstep/jwp/controller/HelloController.java
@@ -10,6 +10,6 @@ public class HelloController extends AbstractController {
     @Override
     protected HttpResponse doGet(HttpRequest request) {
         String responseBody = "Hello world!";
-        return new HttpResponse(HttpStatus.OK, responseBody, ContentType.HTML);
+        return new HttpResponse.Builder(HttpStatus.OK, responseBody, ContentType.HTML).build();
     }
 }
diff --git a/tomcat/src/main/java/nextstep/jwp/controller/LoginController.java b/tomcat/src/main/java/nextstep/jwp/controller/LoginController.java
index 5360d81f0a..93f8cb1253 100644
--- a/tomcat/src/main/java/nextstep/jwp/controller/LoginController.java
+++ b/tomcat/src/main/java/nextstep/jwp/controller/LoginController.java
@@ -31,11 +31,16 @@ protected HttpResponse doGet(HttpRequest request) throws Exception {
         if (loginUser.isPresent()) {
             return redirectByAlreadyLogin(responseBody);
         }
-        return new HttpResponse(HttpStatus.OK, responseBody, ContentType.HTML);
+        return new HttpResponse.Builder(HttpStatus.OK, responseBody, ContentType.HTML)
+                .build();
+
     }
 
     private HttpResponse redirectByAlreadyLogin(String responseBody) {
-        return new HttpResponse(HttpStatus.FOUND, responseBody, ContentType.HTML, "/index.html");
+        return new HttpResponse.Builder(HttpStatus.FOUND, responseBody, ContentType.HTML)
+                .redirect("/index.html")
+                .build();
+
     }
 
     @Override
@@ -58,18 +63,25 @@ private HttpResponse makeLoginResponse(Map<String, String> loginData, final Stri
     }
 
     private HttpResponse successLoginResponse(String responseBody, User user) {
-        HttpResponse httpResponse =
-                new HttpResponse(HttpStatus.FOUND, responseBody, ContentType.HTML, "/index.html");
         Session session = new Session();
         session.setAttribute("user", user);
         SessionManager.add(session);
-        httpResponse.addJSessionId(session);
+        HttpResponse httpResponse =
+                new HttpResponse.Builder(HttpStatus.FOUND, responseBody, ContentType.HTML)
+                        .redirect("index.html")
+                        .addJSessionId(session)
+                        .build();
+
+
         return httpResponse;
     }
 
     private HttpResponse failLoginResponse(String responseBody) {
         log.info("로그인 계정 정보가 이상합니다. responseBody={}", responseBody);
-        return new HttpResponse(HttpStatus.FOUND, responseBody, ContentType.HTML, "/401.html");
+        return new HttpResponse.Builder(HttpStatus.FOUND, responseBody, ContentType.HTML)
+                .redirect("/401.html")
+                .build();
+
     }
 
     private boolean isSuccessLogin(String account, String password) {
diff --git a/tomcat/src/main/java/nextstep/jwp/controller/RegisterController.java b/tomcat/src/main/java/nextstep/jwp/controller/RegisterController.java
index 525ac122d2..d1f365af25 100644
--- a/tomcat/src/main/java/nextstep/jwp/controller/RegisterController.java
+++ b/tomcat/src/main/java/nextstep/jwp/controller/RegisterController.java
@@ -30,7 +30,9 @@ protected HttpResponse doGet(HttpRequest request) throws Exception {
         String requestUrl = request.getRequestUrl();
         Path path = PathFinder.findPath(requestUrl + ".html");
         var responseBody = new String(Files.readAllBytes(path));
-        return new HttpResponse(HttpStatus.OK, responseBody, ContentType.HTML);
+        return new HttpResponse.Builder(HttpStatus.OK, responseBody, ContentType.HTML)
+                .build();
+
     }
 
     @Override
@@ -44,7 +46,11 @@ protected HttpResponse doPost(HttpRequest request) throws Exception {
         saveUser(registerData);
         Path path = PathFinder.findPath(requestUrl + ".html");
         String responseBody = new String(Files.readAllBytes(path));
-        return new HttpResponse(HttpStatus.FOUND, responseBody, ContentType.HTML, "/index.html");
+        return new HttpResponse.Builder(HttpStatus.FOUND, responseBody, ContentType.HTML)
+                .redirect("/index.html")
+                .build();
+
+
     }
 
     private boolean checkInputForm(final HashMap<String, String> registerData) {
@@ -56,7 +62,10 @@ private boolean checkInputForm(final HashMap<String, String> registerData) {
     private HttpResponse generateBadRequestResponse() throws URISyntaxException, IOException {
         Path path = PathFinder.findPath("/400.html");
         String responseBody = new String(Files.readAllBytes(path));
-        return new HttpResponse(HttpStatus.FOUND, responseBody, ContentType.HTML, "/400.html");
+        return new HttpResponse.Builder(HttpStatus.FOUND, responseBody, ContentType.HTML)
+                .redirect("/400.html")
+                .build();
+
     }
 
     private void saveUser(HashMap<String, String> registerData) {
diff --git a/tomcat/src/main/java/org/apache/catalina/connector/Connector.java b/tomcat/src/main/java/org/apache/catalina/connector/Connector.java
index 3b2c4dda7c..7c5f8e379f 100644
--- a/tomcat/src/main/java/org/apache/catalina/connector/Connector.java
+++ b/tomcat/src/main/java/org/apache/catalina/connector/Connector.java
@@ -8,6 +8,9 @@
 import java.io.UncheckedIOException;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 
 public class Connector implements Runnable {
 
@@ -15,17 +18,22 @@ public class Connector implements Runnable {
 
     private static final int DEFAULT_PORT = 8080;
     private static final int DEFAULT_ACCEPT_COUNT = 100;
+    private static final int DEFAULT_MAX_THREADS = 200;
+
+    private static final int TERMINATION_LIMIT_SECONDS = 60;
 
     private final ServerSocket serverSocket;
+    private final ExecutorService executorService;
     private boolean stopped;
 
     public Connector() {
-        this(DEFAULT_PORT, DEFAULT_ACCEPT_COUNT);
+        this(DEFAULT_PORT, DEFAULT_ACCEPT_COUNT, DEFAULT_MAX_THREADS);
     }
 
-    public Connector(final int port, final int acceptCount) {
+    public Connector(final int port, final int acceptCount, final int maxThreads) {
         this.serverSocket = createServerSocket(port, acceptCount);
         this.stopped = false;
+        this.executorService = Executors.newFixedThreadPool(maxThreads);
     }
 
     private ServerSocket createServerSocket(final int port, final int acceptCount) {
@@ -67,15 +75,27 @@ private void process(final Socket connection) {
             return;
         }
         var processor = new Http11Processor(connection);
-        new Thread(processor).start();
+        executorService.execute(processor);
     }
 
     public void stop() {
         stopped = true;
         try {
+            executorService.shutdown();
+            terminateWhenTimeLimitExceed();
             serverSocket.close();
         } catch (IOException e) {
             log.error(e.getMessage(), e);
+        } catch (InterruptedException e) {
+            executorService.shutdownNow();
+            log.error(e.getMessage(), e);
+            Thread.currentThread().interrupt();
+        }
+    }
+
+    private void terminateWhenTimeLimitExceed() throws InterruptedException {
+        if (!executorService.awaitTermination(TERMINATION_LIMIT_SECONDS, TimeUnit.SECONDS)) {
+            executorService.shutdownNow();
         }
     }
 
diff --git a/tomcat/src/main/java/org/apache/coyote/http11/Http11Processor.java b/tomcat/src/main/java/org/apache/coyote/http11/Http11Processor.java
index 7b3d6f9033..bbe55775f1 100644
--- a/tomcat/src/main/java/org/apache/coyote/http11/Http11Processor.java
+++ b/tomcat/src/main/java/org/apache/coyote/http11/Http11Processor.java
@@ -21,13 +21,6 @@
 public class Http11Processor implements Runnable, Processor {
 
     private static final Logger log = LoggerFactory.getLogger(Http11Processor.class);
-    private static final String ACCOUNT_KEY = "account";
-    private static final String PASSWORD_KEY = "password";
-    private static final String EMAIL_KEY = "email";
-    private static final String INDEX_PAGE = "/index.html";
-    private static final String LOGIN_PAGE = "/login.html";
-    private static final String UNAUTHORIZED_PAGE = "/401.html";
-    private static final String REGISTER_PAGE = "/register.html";
 
     private final Socket connection;
 
@@ -64,7 +57,10 @@ private HttpResponse makeResponse(HttpRequest httpRequest) throws Exception {
         } catch (IllegalArgumentException e) {
             Path path = PathFinder.findPath("/400.html");
             String responseBody = new String(Files.readAllBytes(path));
-            return new HttpResponse(HttpStatus.FOUND, responseBody, ContentType.HTML, "/400.html");
+            return new HttpResponse.Builder(HttpStatus.FOUND, responseBody, ContentType.HTML)
+                    .redirect("/400.html")
+                    .build();
         }
+
     }
 }
diff --git a/tomcat/src/main/java/org/apache/coyote/http11/response/HttpResponse.java b/tomcat/src/main/java/org/apache/coyote/http11/response/HttpResponse.java
index e4318eef7e..f1e05c6d2d 100644
--- a/tomcat/src/main/java/org/apache/coyote/http11/response/HttpResponse.java
+++ b/tomcat/src/main/java/org/apache/coyote/http11/response/HttpResponse.java
@@ -13,34 +13,41 @@ public class HttpResponse {
     private final Map<String, String> headers;
     private final String responseBody;
 
-    public HttpResponse(HttpStatus httpStatus, String responseBody,
-                        ContentType contentType, String redirectUrl) {
-        this.startLine = new ResponseLine(httpStatus);
-        this.headers = new LinkedHashMap<>();
-        initHeader(contentType, responseBody, redirectUrl);
-        this.responseBody = responseBody;
+    private HttpResponse(Builder builder) {
+        this.startLine = builder.startLine;
+        this.headers = builder.headers;
+        this.responseBody = builder.responseBody;
     }
 
+    public static class Builder {
+        private ResponseLine startLine;
+        private Map<String, String> headers = new LinkedHashMap<>();
+        private String responseBody;
 
-    public HttpResponse(final HttpStatus httpStatus, final String responseBody, final ContentType contentType) {
-        this.startLine = new ResponseLine(httpStatus);
-        this.headers = new LinkedHashMap<>();
-        initHeader(contentType, responseBody);
-        this.responseBody = responseBody;
-    }
+        public Builder(HttpStatus httpStatus, String responseBody, ContentType contentType) {
+            this.startLine = new ResponseLine(httpStatus);
+            this.responseBody = responseBody;
+            initHeader(contentType, responseBody);
+        }
 
-    private void initHeader(final ContentType contentType, final String responseBody, final String redirectUrl) {
-        initHeader(contentType, responseBody);
-        headers.put("Location", redirectUrl);
-    }
+        public Builder redirect(String redirectUrl) {
+            headers.put("Location", redirectUrl);
+            return this;
+        }
 
-    private void initHeader(ContentType contentType, String responseBody) {
-        headers.put("Content-Type", contentType.getContentType() + ";charset=utf-8");
-        headers.put("Content-Length", String.valueOf(responseBody.getBytes(StandardCharsets.UTF_8).length));
-    }
+        public Builder addJSessionId(Session session) {
+            headers.put("Set-Cookie", "JSESSIONID=" + session.getId());
+            return this;
+        }
+
+        public HttpResponse build() {
+            return new HttpResponse(this);
+        }
 
-    public void addJSessionId(final Session session) {
-        headers.put("Set-Cookie", "JSESSIONID=" + session.getId());
+        private void initHeader(ContentType contentType, String responseBody) {
+            headers.put("Content-Type", contentType.getContentType() + ";charset=utf-8");
+            headers.put("Content-Length", String.valueOf(responseBody.getBytes(StandardCharsets.UTF_8).length));
+        }
     }
 
     @Override
diff --git a/tomcat/src/main/java/org/apache/coyote/http11/session/Session.java b/tomcat/src/main/java/org/apache/coyote/http11/session/Session.java
index 6cf0f95bb9..ceb0789e59 100644
--- a/tomcat/src/main/java/org/apache/coyote/http11/session/Session.java
+++ b/tomcat/src/main/java/org/apache/coyote/http11/session/Session.java
@@ -1,13 +1,13 @@
 package org.apache.coyote.http11.session;
 
-import java.util.HashMap;
 import java.util.Map;
 import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 
 public class Session {
 
     private final String id;
-    private final Map<String, Object> values = new HashMap<>();
+    private final Map<String, Object> values = new ConcurrentHashMap<>();
 
     public Session() {
         this.id = UUID.randomUUID().toString();
diff --git a/tomcat/src/main/java/org/apache/coyote/http11/session/SessionManager.java b/tomcat/src/main/java/org/apache/coyote/http11/session/SessionManager.java
index 0d9034a98c..9ed11fffb9 100644
--- a/tomcat/src/main/java/org/apache/coyote/http11/session/SessionManager.java
+++ b/tomcat/src/main/java/org/apache/coyote/http11/session/SessionManager.java
@@ -3,14 +3,14 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 public class SessionManager {
 
     private static final Logger log = LoggerFactory.getLogger(SessionManager.class);
 
-    private static final Map<String, Session> SESSIONS = new HashMap<>();
+    private static final Map<String, Session> SESSIONS = new ConcurrentHashMap<>();
 
     public static void add(Session session) {
         log.info("session add 완료: {}", session.getId());
diff --git a/tomcat/src/main/java/org/apache/coyote/http11/util/PathFinder.java b/tomcat/src/main/java/org/apache/coyote/http11/util/PathFinder.java
index 5f4624abf5..206e453e79 100644
--- a/tomcat/src/main/java/org/apache/coyote/http11/util/PathFinder.java
+++ b/tomcat/src/main/java/org/apache/coyote/http11/util/PathFinder.java
@@ -9,9 +9,17 @@ public class PathFinder {
 
     private static final String RESOURCE_ROOT_DIRECTORY_PATH = "static";
 
-    public static Path findPath(String resourceName) throws URISyntaxException {
-        final URL resource =
-                PathFinder.class.getClassLoader().getResource(RESOURCE_ROOT_DIRECTORY_PATH + resourceName);
-        return Paths.get(resource.toURI());
+    public static Path findPath(String resourceName) {
+        try {
+            URL resource =
+                    PathFinder.class.getClassLoader().getResource(RESOURCE_ROOT_DIRECTORY_PATH + resourceName);
+
+            if (resource == null) {
+                throw new IllegalArgumentException("Resource Not Found: " + resourceName);
+            }
+            return Paths.get(resource.toURI());
+        } catch (URISyntaxException e) {
+            throw new RuntimeException("URI Syntax Exception : " + resourceName);
+        }
     }
 }
diff --git a/tomcat/src/main/java/org/apache/coyote/http11/util/QueryParamsParser.java b/tomcat/src/main/java/org/apache/coyote/http11/util/QueryParamsParser.java
index a15d5a0f55..0204fa802c 100644
--- a/tomcat/src/main/java/org/apache/coyote/http11/util/QueryParamsParser.java
+++ b/tomcat/src/main/java/org/apache/coyote/http11/util/QueryParamsParser.java
@@ -21,8 +21,9 @@ public static HashMap<String, String> parseByBody(final String requestBody) {
 
     private static void initData(final Map<String, String> data, final String[] params) {
         for (final String param : params) {
-            final String paramInfo = param.split("=")[PARAM_INFO_INDEX];
-            final String paramValue = param.split("=")[PARAM_VALUE_INDEX];
+            String[] split = param.split("=");
+            final String paramInfo = split[PARAM_INFO_INDEX];
+            final String paramValue = split[PARAM_VALUE_INDEX];
             data.put(paramInfo, paramValue);
         }
     }
diff --git a/tomcat/src/main/resources/static/400.html b/tomcat/src/main/resources/static/400.html
new file mode 100644
index 0000000000..9e46139a97
--- /dev/null
+++ b/tomcat/src/main/resources/static/400.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Error 400 - Bad Request</title>
+    <style>
+        body {
+            font-family: Arial, sans-serif;
+            text-align: center;
+            background-color: #f7f7f7;
+            margin: 0;
+            padding: 0;
+        }
+        .container {
+            max-width: 600px;
+            margin: 0 auto;
+            padding: 20px;
+            background-color: #fff;
+            border: 1px solid #ddd;
+            border-radius: 5px;
+            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
+        }
+        h1 {
+            color: #ff6347;
+        }
+        p {
+            font-size: 18px;
+        }
+
+    </style>
+</head>
+<body>
+<div class="container">
+    <h1>Error 400 - Bad Request</h1>
+    <p>The request you made was malformed or invalid.</p>
+</div>
+</body>
+</html>