diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2d53e4d6..be329d2c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,7 +17,7 @@ jobs:
 
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip
+        python -m pip install -U pip
         pip install flake8
 
     - name: Lint with flake8
@@ -25,7 +25,7 @@ jobs:
         # stop the build if there are Python syntax errors or undefined names
         flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
-        flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+        flake8 . --count --statistics
 
   pre-commit:
 
@@ -46,7 +46,7 @@ jobs:
 
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip
+        python -m pip install -U pip
         pip install -U setuptools
         pip install pre-commit
 
@@ -72,7 +72,7 @@ jobs:
 
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip
+        python -m pip install -U pip
         pip install -U setuptools
         pip install -e .[testing]
 
diff --git a/optimade_client/informational.py b/optimade_client/informational.py
index d0998790..94556382 100644
--- a/optimade_client/informational.py
+++ b/optimade_client/informational.py
@@ -1,13 +1,14 @@
 import logging
 import os
 from pathlib import Path
+import shutil
 from typing import Union
 from urllib.parse import urlencode
 
 import ipywidgets as ipw
 
-from optimade_client.logger import LOGGER, WIDGET_HANDLER, REPORT_HANDLER
-from optimade_client.utils import __optimade_version__, ButtonStyle
+from optimade_client.logger import LOG_DIR, LOGGER, REPORT_HANDLER, WIDGET_HANDLER
+from optimade_client.utils import __optimade_version__, ButtonStyle, CACHE_DIR
 
 
 IMG_DIR = Path(__file__).parent.joinpath("img")
@@ -244,16 +245,54 @@ def __init__(self, **kwargs):
             description="Show DEBUG messages",
             disabled=False,
             indent=False,
+            width="auto",
+            height="auto",
+        )
+        self.clear_cache = ipw.Button(
+            description="Clear cache",
+            disabled=False,
+            tooltip="Clear cached responses (not logs)",
+            icon="cube",
+            layout={
+                "visibility": "visible" if self._debug else "hidden",
+                "width": "auto",
+            },
+        )
+        self.clear_logs = ipw.Button(
+            description="Clear logs",
+            disabled=False,
+            tooltip="Clear all log history",
+            icon="edit",
+            layout={
+                "visibility": "visible" if self._debug else "hidden",
+                "width": "auto",
+            },
         )
         self.log_output = WIDGET_HANDLER.get_widget()
         super().__init__(
-            children=(ipw.VBox(children=(self.toggle_debug, self.log_output)),),
+            children=(
+                ipw.VBox(
+                    children=(
+                        ipw.HBox(
+                            children=(
+                                self.toggle_debug,
+                                self.clear_cache,
+                                self.clear_logs,
+                            ),
+                            layout={"height": "auto", "width": "auto"},
+                        ),
+                        self.log_output,
+                    )
+                ),
+            ),
             **kwargs,
         )
         self.set_title(0, "Log")
-        self.selected_index = None
+        self.selected_index = 0 if self._debug else None
 
         self.toggle_debug.observe(self._toggle_debug_logging, names="value")
+        self.clear_cache.on_click(self._clear_cache)
+        self.clear_logs.on_click(self._clear_logs)
 
     def freeze(self):
         """Disable widget"""
@@ -272,16 +311,68 @@ def reset(self):
         self.toggle_debug.disabled = False
         self.log_output.reset()
 
-    @staticmethod
-    def _toggle_debug_logging(change: dict):
+    def _toggle_debug_logging(self, change: dict):
         """Set logging level depending on toggle button"""
         if change["new"]:
             # Set logging level DEBUG
             WIDGET_HANDLER.setLevel(logging.DEBUG)
             LOGGER.info("Set log output in widget to level DEBUG")
             LOGGER.debug("This should now be shown")
+
+            # Show debug buttons
+            self.clear_cache.layout.visibility = "visible"
+            self.clear_logs.layout.visibility = "visible"
         else:
             # Set logging level to INFO
             WIDGET_HANDLER.setLevel(logging.INFO)
             LOGGER.info("Set log output in widget to level INFO")
             LOGGER.debug("This should now NOT be shown")
+
+            # Hide debug buttons
+            self.clear_cache.layout.visibility = "hidden"
+            self.clear_logs.layout.visibility = "hidden"
+
+    @staticmethod
+    def _clear_cache(_):
+        """Clear cached responses (not logs)"""
+        if str(LOG_DIR).startswith(str(CACHE_DIR)):
+            log_sub_dir = list(Path(str(LOG_DIR)[len(f"{CACHE_DIR}/") :]).parts)
+
+        LOGGER.debug(
+            "Cache dir: %s - Log dir: %s - Log sub dir parts: %s",
+            CACHE_DIR,
+            LOG_DIR,
+            log_sub_dir,
+        )
+
+        for dirpath, dirnames, filenames in os.walk(CACHE_DIR):
+            log_dir_part = log_sub_dir.pop(0) if log_sub_dir else ""
+            if not log_sub_dir:
+                LOGGER.debug(
+                    "No more log sub directory parts. Removing %r from dirnames list.",
+                    log_dir_part,
+                )
+                dirnames.remove(log_dir_part)
+
+            for directory in list(dirnames):
+                if directory == log_dir_part:
+                    continue
+                LOGGER.debug(
+                    "Removing folder: %s", Path(dirpath).joinpath(directory).resolve()
+                )
+                shutil.rmtree(
+                    Path(dirpath).joinpath(directory).resolve(), ignore_errors=True
+                )
+                dirnames.remove(directory)
+            for filename in filenames:
+                LOGGER.debug(
+                    "Removing file: %s", Path(dirpath).joinpath(filename).resolve()
+                )
+                os.remove(Path(dirpath).joinpath(filename).resolve())
+        CACHE_DIR.mkdir(parents=True, exist_ok=True)
+
+    @staticmethod
+    def _clear_logs(_):
+        """Clear all logs"""
+        shutil.rmtree(LOG_DIR, ignore_errors=True)
+        LOG_DIR.mkdir(parents=True, exist_ok=True)
diff --git a/optimade_client/query_filter.py b/optimade_client/query_filter.py
index eab14537..b17205bc 100644
--- a/optimade_client/query_filter.py
+++ b/optimade_client/query_filter.py
@@ -1,7 +1,7 @@
 from typing import Union
-import requests
 import traitlets
 import ipywidgets as ipw
+import requests
 
 try:
     from simplejson import JSONDecodeError
@@ -15,16 +15,18 @@
 from optimade_client.exceptions import BadResource, QueryError
 from optimade_client.logger import LOGGER
 from optimade_client.subwidgets import (
-    StructureDropdown,
     FilterTabs,
     ResultsPageChooser,
+    StructureDropdown,
 )
 from optimade_client.utils import (
     ButtonStyle,
-    perform_optimade_query,
+    check_entry_properties,
     handle_errors,
+    ordered_query_url,
+    perform_optimade_query,
+    SESSION,
     TIMEOUT_SECONDS,
-    check_entry_properties,
 )
 
 
@@ -372,7 +374,11 @@ def _query(self, link: str = None) -> dict:
         # If a complete link is provided, use it straight up
         if link is not None:
             try:
-                response = requests.get(link, timeout=TIMEOUT_SECONDS).json()
+                link = ordered_query_url(link)
+                response = SESSION.get(link, timeout=TIMEOUT_SECONDS)
+                if response.from_cache:
+                    LOGGER.debug("Request to %s was taken from cache !", link)
+                response = response.json()
             except (
                 requests.exceptions.ConnectTimeout,
                 requests.exceptions.ConnectionError,
diff --git a/optimade_client/subwidgets/__init__.py b/optimade_client/subwidgets/__init__.py
index 91a36067..07b373a1 100644
--- a/optimade_client/subwidgets/__init__.py
+++ b/optimade_client/subwidgets/__init__.py
@@ -1,17 +1,17 @@
 # pylint: disable=undefined-variable
-from .filter_inputs import *
-from .multi_checkbox import *
-from .output_summary import *
-from .periodic_table import *
-from .provider_database import *
-from .results import *
+from .filter_inputs import *  # noqa: F403
+from .multi_checkbox import *  # noqa: F403
+from .output_summary import *  # noqa: F403
+from .periodic_table import *  # noqa: F403
+from .provider_database import *  # noqa: F403
+from .results import *  # noqa: F403
 
 
 __all__ = (
-    filter_inputs.__all__  # noqa
-    + multi_checkbox.__all__  # noqa
-    + output_summary.__all__  # noqa
-    + periodic_table.__all__  # noqa
-    + provider_database.__all__  # noqa
-    + results.__all__  # noqa
+    filter_inputs.__all__  # noqa: F405
+    + multi_checkbox.__all__  # noqa: F405
+    + output_summary.__all__  # noqa: F405
+    + periodic_table.__all__  # noqa: F405
+    + provider_database.__all__  # noqa: F405
+    + results.__all__  # noqa: F405
 )
diff --git a/optimade_client/subwidgets/provider_database.py b/optimade_client/subwidgets/provider_database.py
index 9b65d060..ce9ca655 100644
--- a/optimade_client/subwidgets/provider_database.py
+++ b/optimade_client/subwidgets/provider_database.py
@@ -11,20 +11,22 @@
 import requests
 import traitlets
 
-from optimade.models import LinksResourceAttributes, LinksResource
+from optimade.models import LinksResource, LinksResourceAttributes
 from optimade.models.links import LinkType
 
-from optimade_client.exceptions import QueryError, OptimadeClientError
+from optimade_client.exceptions import OptimadeClientError, QueryError
 from optimade_client.logger import LOGGER
 from optimade_client.subwidgets.results import ResultsPageChooser
 from optimade_client.utils import (
     get_list_of_valid_providers,
     get_versioned_base_url,
     handle_errors,
+    ordered_query_url,
     perform_optimade_query,
-    validate_api_version,
+    SESSION,
     TIMEOUT_SECONDS,
     update_old_links_resources,
+    validate_api_version,
 )
 
 
@@ -453,7 +455,11 @@ def _query(  # pylint: disable=too-many-locals,too-many-branches,too-many-statem
                         f"?{parsed_query}"
                     )
 
-                response = requests.get(link, timeout=TIMEOUT_SECONDS).json()
+                link = ordered_query_url(link)
+                response = SESSION.get(link, timeout=TIMEOUT_SECONDS)
+                if response.from_cache:
+                    LOGGER.debug("Request to %s was taken from cache !", link)
+                response = response.json()
             except (
                 requests.exceptions.ConnectTimeout,
                 requests.exceptions.ConnectionError,
@@ -641,13 +647,13 @@ def _on_database_change(self, change):
     def _update_provider(self):
         """Update provider summary"""
         html_text = f"""<strong style="line-height:1;{self.text_style}">{getattr(self.provider, 'name', 'Provider')}</strong>
-        <p style="line-height:1.2;{self.text_style}">{getattr(self.provider, 'description', '')}</p>"""
+<p style="line-height:1.2;{self.text_style}">{getattr(self.provider, 'description', '')}</p>"""
         self.provider_summary.value = html_text
 
     def _update_database(self):
         """Update database summary"""
         html_text = f"""<strong style="line-height:1;{self.text_style}">{getattr(self.database, 'name', 'Database')}</strong>
-        <p style="line-height:1.2;{self.text_style}">{getattr(self.database, 'description', '')}</p>"""
+<p style="line-height:1.2;{self.text_style}">{getattr(self.database, 'description', '')}</p>"""
         self.database_summary.value = html_text
 
     def freeze(self):
diff --git a/optimade_client/utils.py b/optimade_client/utils.py
index 5b4322a8..b61561d2 100644
--- a/optimade_client/utils.py
+++ b/optimade_client/utils.py
@@ -1,8 +1,9 @@
+from collections import OrderedDict
 from enum import Enum
 from pathlib import Path
 import re
 from typing import Tuple, List, Union, Iterable
-from urllib.parse import urlencode
+from urllib.parse import urlencode, urlparse, urlunparse, parse_qs
 
 try:
     import simplejson as json
@@ -12,6 +13,9 @@
 from json import JSONDecodeError
 
 import appdirs
+from cachecontrol import CacheControlAdapter
+from cachecontrol.caches.file_cache import FileCache
+from cachecontrol.heuristics import ExpiresAfter
 from pydantic import ValidationError, AnyUrl  # pylint: disable=no-name-in-module
 import requests
 
@@ -40,6 +44,16 @@
 CACHE_DIR.mkdir(parents=True, exist_ok=True)
 CACHED_PROVIDERS = CACHE_DIR / "cached_providers.json"
 
+SESSION = requests.Session()
+SESSION_ADAPTER = CacheControlAdapter(
+    cache=FileCache(CACHE_DIR / ".requests_cache"), heuristic=ExpiresAfter(days=1)
+)
+SESSION_ADAPTER_DEBUG = CacheControlAdapter()
+SESSION.mount("http://", SESSION_ADAPTER)
+SESSION.mount("https://", SESSION_ADAPTER)
+SESSION.mount("http://localhost", SESSION_ADAPTER_DEBUG)
+SESSION.mount("http://127.0.0.1", SESSION_ADAPTER_DEBUG)
+
 
 class ButtonStyle(Enum):
     """Enumeration of button styles"""
@@ -65,7 +79,7 @@ def perform_optimade_query(  # pylint: disable=too-many-arguments,too-many-branc
     page_number: int = None,
 ) -> dict:
     """Perform query of database"""
-    queries = {}
+    queries = OrderedDict()
 
     if endpoint is None:
         endpoint = "/structures"
@@ -115,7 +129,9 @@ def perform_optimade_query(  # pylint: disable=too-many-arguments,too-many-branc
     complete_url = f"{url_path}?{url_query}"
     LOGGER.debug("Performing OPTIMADE query:\n%s", complete_url)
     try:
-        response = requests.get(complete_url, timeout=TIMEOUT_SECONDS)
+        response = SESSION.get(complete_url, timeout=TIMEOUT_SECONDS)
+        if response.from_cache:
+            LOGGER.debug("Request to %s was taken from cache !", complete_url)
     except (
         requests.exceptions.ConnectTimeout,
         requests.exceptions.ConnectionError,
@@ -273,7 +289,9 @@ def get_versioned_base_url(  # pylint: disable=too-many-branches
         f"{base_url}versions" if base_url.endswith("/") else f"{base_url}/versions"
     )
     try:
-        response = requests.get(versions_endpoint, timeout=TIMEOUT_SECONDS)
+        response = SESSION.get(versions_endpoint, timeout=TIMEOUT_SECONDS)
+        if response.from_cache:
+            LOGGER.debug("Request to %s was taken from cache !", versions_endpoint)
     except (
         requests.exceptions.ConnectTimeout,
         requests.exceptions.ConnectionError,
@@ -312,9 +330,13 @@ def get_versioned_base_url(  # pylint: disable=too-many-branches
             base_url + version[1:] if base_url.endswith("/") else base_url + version
         )
         try:
-            response = requests.get(
+            response = SESSION.get(
                 f"{versioned_base_url}/info", timeout=timeout_seconds
             )
+            if response.from_cache:
+                LOGGER.debug(
+                    "Request to %s/info was taken from cache !", versioned_base_url
+                )
         except (
             requests.exceptions.ConnectTimeout,
             requests.exceptions.ConnectionError,
@@ -416,7 +438,9 @@ def get_structures_schema(base_url: str) -> dict:
     )
 
     try:
-        response = requests.get(url_path, timeout=TIMEOUT_SECONDS)
+        response = SESSION.get(url_path, timeout=TIMEOUT_SECONDS)
+        if response.from_cache:
+            LOGGER.debug("Request to %s was taken from cache !", url_path)
     except (
         requests.exceptions.ConnectTimeout,
         requests.exceptions.ConnectionError,
@@ -609,3 +633,23 @@ def update_old_links_resources(resource: dict) -> Union[LinksResource, None]:
             return res
     else:
         return res
+
+
+def ordered_query_url(url: str) -> str:
+    """Decode URL, sort queries, re-encode URL"""
+    parsed_url = urlparse(url)
+    queries = parse_qs(parsed_url.query)
+
+    sorted_keys = sorted(queries.keys())
+
+    res = OrderedDict()
+    for key in sorted_keys:
+        # Since the values are all lists, we also sort these
+        res[key] = sorted(queries[key])
+
+    res = urlencode(res)
+    res = (
+        f"{parsed_url.scheme}://{parsed_url.netloc}{parsed_url.path};{parsed_url.params}?{res}"
+        f"#{parsed_url.fragment}"
+    )
+    return urlunparse(urlparse(res))
diff --git a/requirements.txt b/requirements.txt
index dc38b49b..adba9bd9 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,7 @@
 appdirs~=1.4.4
 appmode~=0.8.0
 ase~=3.20
+cachecontrol[filecache]~=0.12.6
 click~=7.1
 ipywidgets~=7.5
 jupyterlab~=2.2
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 00000000..2f584c74
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,8 @@
+[flake8]
+ignore =
+    # Line to long. Handled by black.
+    E501
+    # Line break before binary operator. This is preferred formatting for black.
+    W503
+    # Whitespace before ':'
+    E203
diff --git a/tasks.py b/tasks.py
index 67c6c907..952defea 100644
--- a/tasks.py
+++ b/tasks.py
@@ -13,7 +13,9 @@
 def update_file(filename: str, sub_line: Tuple[str, str], strip: str = None):
     """Utility function for tasks to read, update, and write files"""
     with open(filename, "r") as handle:
-        lines = [re.sub(sub_line[0], sub_line[1], l.rstrip(strip)) for l in handle]
+        lines = [
+            re.sub(sub_line[0], sub_line[1], line.rstrip(strip)) for line in handle
+        ]
 
     with open(filename, "w") as handle:
         handle.write("\n".join(lines))