diff --git a/src/cert_manager.py b/src/cert_manager.py
index 7128c77..d3eb795 100644
--- a/src/cert_manager.py
+++ b/src/cert_manager.py
@@ -6,7 +6,7 @@ import subprocess
 import typing
 
 if typing.TYPE_CHECKING:
-    from . import params
+    from .params import Parameters
 
 
 class CertManagerError(Exception):
@@ -14,16 +14,24 @@ class CertManagerError(Exception):
 
 
 class CertManager:
+    __slots__ = [
+        "certbot_conf",
+        "certbot_www",
+        "logger",
+        "self_signed_path",
+        "with_certbot",
+    ]
+
     SELF_SIGNED_DAYS = 30
     CRT_FILE = "fullchain.pem"
     KEY_FILE = "privkey.pem"
 
-    def __init__(self, params: params.Parameters) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.certbot_conf = pathlib.Path(params.certbot_conf)
-        self.certbot_www = pathlib.Path(params.certbot_www)
-        self.self_signed_path = pathlib.Path(params.self_signed_path)
-        self.with_certbot = params.with_certbot
+    def __init__(self, params: Parameters) -> None:
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.certbot_conf: pathlib.Path = pathlib.Path(params.certbot_conf)
+        self.certbot_www: pathlib.Path = pathlib.Path(params.certbot_www)
+        self.self_signed_path: pathlib.Path = pathlib.Path(params.self_signed_path)
+        self.with_certbot: bool = params.with_certbot
 
     def init(self, hosts: list[str]) -> None:
         self.logger.debug("Initializing...")
diff --git a/src/data_dir.py b/src/data_dir.py
index f29253b..37a28d0 100644
--- a/src/data_dir.py
+++ b/src/data_dir.py
@@ -10,12 +10,17 @@ if typing.TYPE_CHECKING:
 
 
 class DataDir:
+    __slots__ = [
+        "logger",
+        "root_path",
+    ]
+
     PATH_REGEX = re.compile(r"^[\w-]+$")
     NEEDED_FILES: typing.ClassVar[list[str]] = ["favicon.ico"]
 
     def __init__(self, root_path: str) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.root_path = pathlib.Path(root_path)
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.root_path: pathlib.Path = pathlib.Path(root_path)
 
     def init(self) -> None:
         self.logger.debug("Initializing...")
diff --git a/src/handlers.py b/src/handlers.py
index 4fcb9e2..f989942 100644
--- a/src/handlers.py
+++ b/src/handlers.py
@@ -9,10 +9,14 @@ import re
 import tarfile
 import typing
 
-from . import STAPLER_ASCII, data_dir, logs, project
+from . import STAPLER_ASCII, logs, project
+from .data_dir import DataDir
 
 if typing.TYPE_CHECKING:
-    from . import cert_manager, params, registry, token_manager
+    from .cert_manager import CertManager
+    from .params import Parameters
+    from .registry import Registry
+    from .token_manager import TokenManager
 
 
 class BaseHandler(abc.ABC, http.server.BaseHTTPRequestHandler):
@@ -20,12 +24,14 @@ class BaseHandler(abc.ABC, http.server.BaseHTTPRequestHandler):
     def __init__(
         self,
         *args: typing.Any,
-        params: params.Parameters,
+        params: Parameters,
         **kwargs: dict[str, typing.Any],
     ) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.default_host = params.host.split(":", maxsplit=2)[0]
-        self.out_size = 0
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.default_host: str = params.host.split(":", maxsplit=2)[0]
+        self.out_size: int = 0
+        self._host: str | None = None
+        self._in_size: int | None = None
         super().__init__(*args, **kwargs)
 
     @typing.override
@@ -74,7 +80,7 @@ class BaseHandler(abc.ABC, http.server.BaseHTTPRequestHandler):
             code = color + str(code.value) + logs.TermColor.RESET
         if size == "" and self.out_size > 0:
             size = str(self.out_size)
-        args = (code, self.address_string(), self._get_host(), self.requestline)
+        args = (code, self.address_string(), self.host, self.requestline)
         fmt = "→ %s - %s - %s - %s"
         if size != "":
             args = (*args, size)
@@ -117,10 +123,22 @@ class BaseHandler(abc.ABC, http.server.BaseHTTPRequestHandler):
         self.end_headers()
         self.close_connection = True
 
+    @property
+    def host(self) -> str:
+        if self._host is None:
+            self._host = self._get_host()
+        return self._host
+
     def _get_host(self) -> str:
         host = self._get_header("Host", self.default_host)
         return host.split(":", maxsplit=2)[0]
 
+    @property
+    def in_size(self) -> int:
+        if self._in_size is None:
+            self._in_size = self._get_length()
+        return self._in_size
+
     def _get_length(self) -> int:
         return int(self._get_header("Content-Length", "0"))
 
@@ -137,10 +155,10 @@ class BaseHandler(abc.ABC, http.server.BaseHTTPRequestHandler):
         )
 
     def _pre_log_request(self) -> None:  # pragma: no cover
-        args = ("...", self.address_string(), self._get_host(), self.requestline)
+        args = ("...", self.address_string(), self.host, self.requestline)
         fmt = "← %s - %s - %s - %s"
-        if (size := self._get_length()) > 0:
-            args = (*args, size)
+        if self.in_size > 0:
+            args = (*args, self.in_size)
             fmt += " - %s"
         self.logger.debug(fmt, *args)
 
@@ -163,21 +181,39 @@ class RequestHandler(http.server.SimpleHTTPRequestHandler, BaseHandler):
     def __init__(
         self,
         *args: typing.Any,
-        params: params.Parameters,
-        registry: registry.Registry,
-        cert_manager: cert_manager.CertManager,
-        token_manager: token_manager.TokenManager,
+        params: Parameters,
+        registry: Registry,
+        cert_manager: CertManager,
+        token_manager: TokenManager,
         **kwargs: dict[str, typing.Any],
     ) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.token_manager = token_manager
-        self.data_dir = data_dir.DataDir(params.data_dir)
-        self.max_size_bytes = params.max_size_bytes
-        self.registry = registry
-        self.cert_manager = cert_manager
-        self.certbot_www = os.path.realpath(params.certbot_www)
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.token_manager: TokenManager = token_manager
+        self.data_dir: DataDir = DataDir(params.data_dir)
+        self.max_size_bytes: int = params.max_size_bytes
+        self.registry: Registry = registry
+        self.cert_manager: CertManager = cert_manager
+        self.certbot_www: str = os.path.realpath(params.certbot_www)
+        self._token: str | None = None
+        self._target_host: str | None = None
         super().__init__(*args, directory=params.data_dir, **kwargs, params=params)  # ty:ignore[unknown-argument]
 
+    @property
+    def token(self) -> str:
+        if self._token is None:
+            self._token = self._get_header(self.TOKEN_HEADER)
+        return self._token
+
+    @property
+    def target_host(self) -> str:
+        if self._target_host is None:
+            self._target_host = self._get_header(self.HOST_HEADER).lower()
+        return self._target_host
+
+    @property
+    def has_target_host(self) -> bool:
+        return len(self.target_host) > 0
+
     @typing.override
     def do_HEAD(self) -> None:
         self._pre_log_request()
@@ -186,7 +222,7 @@ class RequestHandler(http.server.SimpleHTTPRequestHandler, BaseHandler):
     @typing.override
     def do_GET(self) -> None:
         self._pre_log_request()
-        if self.path == "/" and self._get_host() == self.default_host:
+        if self.path == "/" and self.host == self.default_host:
             return self.send_basic_body(self.server_signature())
         super().do_GET()
         return None
@@ -195,30 +231,25 @@ class RequestHandler(http.server.SimpleHTTPRequestHandler, BaseHandler):
         self._pre_log_request()
         if (sub_path := self.__check_update_request()) is None:
             return None
-        host: str | None = (
-            self._get_header(self.HOST_HEADER).lower()
-            if self._has_header(self.HOST_HEADER)
-            else None
-        )
-        if host is not None and not self.__valid_host(host):
+        if self.has_target_host and not self.__valid_host(self.target_host):
             return self.send_error(
                 http.HTTPStatus.BAD_REQUEST, "Invalid requested host"
             )
         if (
-            host is not None
-            and (page := self.registry.get_from_host(host)) is not None
+            self.has_target_host
+            and (page := self.registry.get_from_host(self.target_host)) is not None
             and page.path != sub_path
         ):
             return self.send_error(http.HTTPStatus.FORBIDDEN, "Host already taken")
-        if (content_length := self._get_length()) == 0:
+        if self.in_size == 0:
             return self.send_error(http.HTTPStatus.LENGTH_REQUIRED, "No body found")
-        if content_length > self.max_size_bytes:
+        if self.in_size > self.max_size_bytes:
             return self.send_error(
                 http.HTTPStatus.CONTENT_TOO_LARGE,
                 "Archive too large",
             )
         try:
-            file_bytes = io.BytesIO(self.rfile.read(content_length))
+            file_bytes = io.BytesIO(self.rfile.read(self.in_size))
             self.data_dir.extract_tar_bytes(sub_path, file_bytes)
         except tarfile.TarError:
             return self.send_error(http.HTTPStatus.BAD_REQUEST, "Invalid tar archive")
@@ -229,9 +260,11 @@ class RequestHandler(http.server.SimpleHTTPRequestHandler, BaseHandler):
             f"Resource /{sub_path}/ updated",
         )
         self.registry.add(sub_path)
-        self.token_manager.set_token(self._get_header(self.TOKEN_HEADER), sub_path)
-        if host is not None and self.cert_manager.create_or_update(host):
-            self.registry.set_host(sub_path, host)
+        self.token_manager.set_token(self.token, sub_path)
+        if self.has_target_host and self.cert_manager.create_or_update(
+            self.target_host
+        ):
+            self.registry.set_host(sub_path, self.target_host)
         return None
 
     def do_DELETE(self) -> None:
@@ -261,14 +294,12 @@ class RequestHandler(http.server.SimpleHTTPRequestHandler, BaseHandler):
     def translate_path(self, path: str) -> str:
         if path.startswith(self.CERTBOT_CHALLENGE_PATH):
             return self.certbot_www + path
-        host = self._get_host()
         if (
-            host != self.default_host
-            and (page := self.registry.get_from_host(host := self._get_host()))
-            is not None
+            self.host != self.default_host
+            and (page := self.registry.get_from_host(self.host)) is not None
         ):
             path = f"/{page.path}" + path
-        elif host != self.default_host:
+        elif self.host != self.default_host:
             return ""
         elif (
             path not in self.AUTHORIZED_PATHS
@@ -283,14 +314,13 @@ class RequestHandler(http.server.SimpleHTTPRequestHandler, BaseHandler):
         if not self._has_header(self.TOKEN_HEADER):
             self.send_error(http.HTTPStatus.BAD_REQUEST, "No X-Token header in request")
             return None
-        token = self._get_header(self.TOKEN_HEADER)
-        if not self.token_manager.is_valid(token):
+        if not self.token_manager.is_valid(self.token):
             self.send_error(http.HTTPStatus.UNAUTHORIZED, "Invalid token")
             return None
         if (sub_path := self.__get_subpath(self.path, self.UPDATE_PATH_REGEX)) is None:
             self.send_error(http.HTTPStatus.BAD_REQUEST, "Invalid path")
             return None
-        if not self.token_manager.is_valid_for_path(token, sub_path):
+        if not self.token_manager.is_valid_for_path(self.token, sub_path):
             self.send_error(http.HTTPStatus.FORBIDDEN, "Path forbidden for this token")
             return None
         return sub_path
@@ -314,7 +344,7 @@ class UpgradeHandler(BaseHandler):
         self._pre_log_request()
         self.send_status_only(
             http.HTTPStatus.MOVED_PERMANENTLY,
-            headers={"Location": f"https://{self._get_host()}{self.path.lower()}"},
+            headers={"Location": f"https://{self.host}{self.path.lower()}"},
         )
 
     def do_GET(self) -> None:
diff --git a/src/logs.py b/src/logs.py
index 32a54c5..2ce841c 100644
--- a/src/logs.py
+++ b/src/logs.py
@@ -3,7 +3,7 @@ import logging
 import typing
 
 if typing.TYPE_CHECKING:
-    from . import params
+    from .params import Parameters
 
 
 class TermColor(enum.StrEnum):
@@ -54,7 +54,7 @@ class ColoredLoggingFormatter(logging.Formatter):
 
     @typing.override
     def __init__(self, trace: bool) -> None:
-        self.trace = trace
+        self.trace: bool = trace
         super().__init__()
 
     @typing.override
@@ -75,7 +75,7 @@ class ColoredLoggingFormatter(logging.Formatter):
         return formatter.format(record)
 
 
-def setup_logs(params: params.Parameters) -> None:
+def setup_logs(params: Parameters) -> None:
     stream_handler = logging.StreamHandler()
     stream_handler.setFormatter(ColoredLoggingFormatter(trace=params.debug))
     log_level = logging.INFO
diff --git a/src/page.py b/src/page.py
index 7bc397e..d648229 100644
--- a/src/page.py
+++ b/src/page.py
@@ -1,7 +1,7 @@
 import dataclasses
 
 
-@dataclasses.dataclass
+@dataclasses.dataclass(slots=True)
 class Page:
     path: str
     with_index: bool = False
diff --git a/src/params.py b/src/params.py
index a9c6688..531a50d 100644
--- a/src/params.py
+++ b/src/params.py
@@ -8,7 +8,7 @@ from . import project
 __EPILOG = "(Each option can be supplied with equivalent environment variable.)"
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(frozen=True, slots=True)
 class Parameters:
     debug: bool = False
     data_dir: str = "./data"
diff --git a/src/registry.py b/src/registry.py
index b49a8c0..2ae04b9 100644
--- a/src/registry.py
+++ b/src/registry.py
@@ -1,20 +1,27 @@
 import logging
 import typing
 
-from . import data_dir, page
+from .data_dir import DataDir
+from .page import Page
 
 if typing.TYPE_CHECKING:
-    from . import params
+    from .params import Parameters
 
 
 class Registry:
+    __slots__ = [
+        "data_dir",
+        "logger",
+        "pages",
+    ]
+
     HOST_FILE = ".host"
     TOKEN_FILE = ".token"  # noqa: S105
 
-    def __init__(self, params: params.Parameters) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.pages: dict[str, page.Page] = {}
-        self.data_dir = data_dir.DataDir(params.data_dir)
+    def __init__(self, params: Parameters) -> None:
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.pages: dict[str, Page] = {}
+        self.data_dir = DataDir(params.data_dir)
 
     def load_pages(self) -> None:
         self.pages = {}
@@ -25,7 +32,7 @@ class Registry:
         return [p.host for p in self.pages.values() if p.host is not None]
 
     def add(self, path: str) -> None:
-        self.pages[path] = page.Page(
+        self.pages[path] = Page(
             path,
             self.data_dir.has_index(path),
             self.data_dir.get_file(path, self.HOST_FILE),
@@ -51,12 +58,12 @@ class Registry:
             del self.pages[path]
             self.logger.info("Removed %s", page)
 
-    def get_from_path(self, path: str) -> page.Page | None:
+    def get_from_path(self, path: str) -> Page | None:
         if path in self.pages:
             return self.pages[path]
         return None
 
-    def get_from_host(self, host: str) -> page.Page | None:
+    def get_from_host(self, host: str) -> Page | None:
         for p in self.pages.values():
             if p.host == host:
                 return p
diff --git a/src/server.py b/src/server.py
index eecb27e..e532f60 100644
--- a/src/server.py
+++ b/src/server.py
@@ -6,27 +6,38 @@ import typing
 
 from . import (
     STAPLER_ASCII,
-    cert_manager,
-    data_dir,
-    handlers,
     project,
-    registry,
-    token_manager,
 )
+from .cert_manager import CertManager
+from .data_dir import DataDir
+from .handlers import RequestHandler, UpgradeHandler
+from .params import Parameters
+from .registry import Registry
+from .token_manager import TokenManager
 
 if typing.TYPE_CHECKING:
-    from . import params
+    from .params import Parameters
 
 
 class StaplerServer:
-    def __init__(self, params: params.Parameters) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.params = params
-        self.registry = registry.Registry(params)
-        self.cert_manager = cert_manager.CertManager(params)
-        self.token_manager = token_manager.TokenManager(params, self.registry)
-        self.data_dir = data_dir.DataDir(params.data_dir)
-        self.default_host = params.host.split(":", maxsplit=2)[0]
+    __slots__ = [
+        "cert_manager",
+        "data_dir",
+        "default_host",
+        "logger",
+        "params",
+        "registry",
+        "token_manager",
+    ]
+
+    def __init__(self, params: Parameters) -> None:
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.params: Parameters = params
+        self.registry: Registry = Registry(params)
+        self.cert_manager: CertManager = CertManager(params)
+        self.token_manager: TokenManager = TokenManager(params, self.registry)
+        self.data_dir: DataDir = DataDir(params.data_dir)
+        self.default_host: str = params.host.split(":", maxsplit=2)[0]
 
     def __get_all_hosts(self) -> list[str]:
         return [self.default_host, *self.registry.get_hosts()]
@@ -42,7 +53,7 @@ class StaplerServer:
     def __request_handler(  # pragma: no cover
         self, *args: typing.Any
     ) -> http.server.BaseHTTPRequestHandler:
-        return handlers.RequestHandler(
+        return RequestHandler(
             *args,
             params=self.params,
             registry=self.registry,
@@ -83,7 +94,7 @@ class StaplerServer:
     def __upgrade_handler(  # pragma: no cover
         self, *args: typing.Any
     ) -> http.server.BaseHTTPRequestHandler:
-        return handlers.UpgradeHandler(
+        return UpgradeHandler(
             *args,
             params=self.params,
         )
diff --git a/src/token_manager.py b/src/token_manager.py
index e388b5c..9c52671 100644
--- a/src/token_manager.py
+++ b/src/token_manager.py
@@ -7,17 +7,26 @@ import typing
 from . import project
 
 if typing.TYPE_CHECKING:
-    from . import params, registry
+    from .params import Parameters
+    from .registry import Registry
 
 
 class TokenManager:
+    __slots__ = [
+        "logger",
+        "registry",
+        "token_hashes",
+        "token_salt",
+        "tokens_file",
+    ]
+
     FILE = ".tokens"
 
-    def __init__(self, params: params.Parameters, registry: registry.Registry) -> None:
-        self.logger = logging.getLogger(self.__class__.__name__)
-        self.token_salt = params.token_salt
-        self.tokens_file = pathlib.Path(params.data_dir) / self.FILE
-        self.registry = registry
+    def __init__(self, params: Parameters, registry: Registry) -> None:
+        self.logger: logging.Logger = logging.getLogger(self.__class__.__name__)
+        self.token_salt: str = params.token_salt
+        self.tokens_file: pathlib.Path = pathlib.Path(params.data_dir) / self.FILE
+        self.registry: Registry = registry
         self.token_hashes: list[str] = []
 
     def init(self) -> None:
diff --git a/tests/__init__.py b/tests/__init__.py
index ed71692..6aaa51f 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -11,7 +11,7 @@ class BaseTestCase(unittest.TestCase):
     def __init__(self, *args: typing.Any, **kwargs: typing.Any) -> None:
         self.mocks: list[unittest.mock.Mock] = []
         self.tmp_dir: tempfile.TemporaryDirectory | None = None
-        self.tmp_path = pathlib.Path()
+        self.tmp_path: pathlib.Path = pathlib.Path()
         super().__init__(*args, **kwargs)
 
     @typing.override