diff --git a/ash.py b/ash.py
index bb3aae2..205b602 100644
--- a/ash.py
+++ b/ash.py
@@ -10,6 +10,8 @@
 from urllib.parse import urlsplit
 from collections.abc import Mapping
 
+from collections.abc import Iterator
+
 import flask
 import requests
 from elasticsearch import Elasticsearch
@@ -22,10 +24,7 @@ class DefaultConfig:
     T_EXTERNAL_TWEETS = False
 
 
-app = flask.Flask(
-    __name__,
-    static_url_path='/tweet/static'
-)
+app = flask.Flask(__name__, static_url_path='/tweet/static')
 app.config.from_object(DefaultConfig)
 try:
     app.config.from_object('config.Config')
@@ -35,7 +34,6 @@ class DefaultConfig:
 
 # Set up external Tweets support
 if app.config.get('T_EXTERNAL_TWEETS'):
-
     # https://developer.twitter.com/en/docs/basics/authentication/api-reference/token
     resp = requests.post(
         'https://api.twitter.com/oauth2/token',
@@ -51,7 +49,7 @@ class DefaultConfig:
     app.config['T_TWITTER_TOKEN'] = bearer_token
 
 
-def toot_to_tweet(status):
+def toot_to_tweet(status: dict) -> dict:
     '''Transform toot to be compatible with tweet-interface'''
     # Status is a tweet
     if status.get('user'):
@@ -82,36 +80,33 @@ def toot_to_tweet(status):
 
 class TweetsDatabase(Mapping):
 
-    def __init__(self, es_host, es_index):
+    def __init__(self, es_host: str, es_index: str) -> None:
         self.es = Elasticsearch(es_host)
         self.es_index = es_index
 
-    def _search(self, **kwargs):
+    def _search(self, **kwargs) -> Iterator[dict]:
         if not kwargs.get('index'):
             kwargs['index'] = self.es_index
         hits = self.es.search(**kwargs)['hits']['hits']
-        tweets = []
         for hit in hits:
             tweet = hit['_source']
             tweet['@index'] = hit['_index']
             tweet = toot_to_tweet(tweet)
-            tweets.append(tweet)
-        return tweets
+            yield tweet
 
-    def __getitem__(self, tweet_id):
+    def __getitem__(self, tweet_id: str | int) -> dict:
         resp = self._search(
             query={
                 'term': {
                     '_id': tweet_id
                 }
             })
-        if len(resp) == 0:
-            raise KeyError(f'Tweet ID {tweet_id} not found')
-        else:
-            tweet = resp[0]
-        return tweet
+        try:
+            return next(resp)
+        except StopIteration:
+            raise KeyError(f'Tweet ID {tweet_id} not found') from None
 
-    def __iter__(self):
+    def __iter__(self) -> Iterator[int]:
         resp = self._search(
             sort=['@timestamp'],
             #size=1000,
@@ -119,7 +114,7 @@ def __iter__(self):
         for tweet in resp:
             yield tweet['id']
 
-    def __reversed__(self):
+    def __reversed__(self) -> Iterator[int]:
         resp = self._search(
             sort=[{
                 '@timestamp': {'order': 'desc'}
@@ -129,10 +124,10 @@ def __reversed__(self):
         for tweet in resp:
             yield tweet['id']
 
-    def __len__(self):
+    def __len__(self) -> int:
         return self.es.count(index=self.es_index)['count']
 
-    def search(self, *, keyword=None, user_screen_name=None, index=None, limit=100):
+    def search(self, *, keyword=None, user_screen_name=None, index=None, limit=100) -> Iterator[dict]:
         keyword_query = {
             'simple_query_string': {
                 'query': keyword,
@@ -142,7 +137,7 @@ def search(self, *, keyword=None, user_screen_name=None, index=None, limit=100):
         }
         if user_screen_name and '@' in user_screen_name:  # Mastodon
             screen_name_field = 'account.fqn.keyword'
-        else:
+        else:  # Twitter
             screen_name_field = 'user.screen_name.keyword'
         user_query = {
             'term': {
@@ -166,7 +161,7 @@ def search(self, *, keyword=None, user_screen_name=None, index=None, limit=100):
         )
         return resp
 
-    def get_users(self):
+    def get_users(self) -> Iterator[dict]:
         agg_name_twitter = 'user_screen_names'
         agg_name_mastodon = 'account_fqn'
         resp = self.es.search(
@@ -186,16 +181,14 @@ def get_users(self):
             },
         )
         buckets = resp['aggregations'][agg_name_twitter]['buckets'] + resp['aggregations'][agg_name_mastodon]['buckets']
-        users = [
-            {
+        for bucket in buckets:
+            user = {
                 'screen_name': bucket['key'],
                 'tweets_count': bucket['doc_count']
             }
-            for bucket in buckets
-        ]
-        return users
+            yield user
 
-    def get_indexes(self):
+    def get_indexes(self) -> Iterator[dict]:
         agg_name = 'index_names'
         resp = self.es.search(
             index=self.es_index,
@@ -208,17 +201,15 @@ def get_indexes(self):
                 }
             },
         )
-        indexes = [
-            {
+        for bucket in resp['aggregations'][agg_name]['buckets']:
+            index = {
                 'name': bucket['key'],
                 'tweets_count': bucket['doc_count']
             }
-            for bucket in resp['aggregations'][agg_name]['buckets']
-        ]
-        return indexes
+            yield index
 
 
-def get_tdb():
+def get_tdb() -> TweetsDatabase:
     if not hasattr(flask.g, 'tdb'):
         flask.g.tdb = TweetsDatabase(
             app.config['T_ES_HOST'],
@@ -228,7 +219,7 @@ def get_tdb():
 
 
 @app.template_global('get_tweet_link')
-def get_tweet_link(screen_name, tweet_id, original_link=False):
+def get_tweet_link(screen_name: str, tweet_id: str | int, original_link: bool = False) -> str:
     if original_link:
         return f'https://twitter.com/{screen_name}/status/{tweet_id}'
     else:
@@ -236,8 +227,7 @@ def get_tweet_link(screen_name, tweet_id, original_link=False):
 
 
 @app.template_filter('format_tweet_text')
-def format_tweet_text(tweet):
-
+def format_tweet_text(tweet: dict) -> str:
     try:
         tweet_text = tweet['full_text']
     except KeyError:
@@ -286,15 +276,13 @@ def format_tweet_text(tweet):
     # true and has a valid "retweeted_status". Tweets that are ingested via
     # Twitter Archive always has "retweeted" set to false (identical to a
     # "traditional" RT.
-    retweeted_status = tweet.get('retweeted_status')
-    if retweeted_status:
+    if retweeted_status := tweet.get('retweeted_status'):
         link = get_tweet_link('status', retweeted_status['id'])
         a = f'<a href="{link}">RT</a>'
         tweet_text = tweet_text.replace('RT', a, 1)
 
     # Format reblogged toot
-    reblogged_status = tweet.get('reblog')
-    if reblogged_status:
+    if reblogged_status := tweet.get('reblog'):
         status_link = reblogged_status['url']
         author = reblogged_status['account']['fqn']
         author_link = reblogged_status['account']['url']
@@ -305,7 +293,7 @@ def format_tweet_text(tweet):
 
 
 @app.template_filter('format_created_at')
-def format_created_at(timestamp, fmt):
+def format_created_at(timestamp: str, fmt: str) -> str:
     try:
         dt = datetime.strptime(timestamp, '%a %b %d %H:%M:%S %z %Y')
     except ValueError:
@@ -317,7 +305,7 @@ def format_created_at(timestamp, fmt):
 
 
 @app.template_filter('in_reply_to_link')
-def in_reply_to_link(tweet):
+def in_reply_to_link(tweet: dict) -> str:
     if tweet.get('account'):  # Mastodon
         # If this is a self-thread, return local link
         if tweet['in_reply_to_account_id'] == tweet['account']['id']:
@@ -329,7 +317,7 @@ def in_reply_to_link(tweet):
         return get_tweet_link('status', tweet['in_reply_to_status_id'])
 
 
-def replace_media_url(url):
+def replace_media_url(url: str) -> str:
     if app.config['T_MEDIA_FROM'] == 'direct':
         return url
     elif app.config['T_MEDIA_FROM'] == 'filesystem':
@@ -343,6 +331,8 @@ def replace_media_url(url):
                 return url.replace(orig, repl)
         else:
             return url
+    else:
+        return url
 
 
 @app.route('/')
@@ -352,11 +342,9 @@ def root():
 
 @app.route('/tweet/')
 def index():
-
     tdb = get_tdb()
     total_tweets = len(tdb)
-    default_user = app.config.get('T_DEFAULT_USER')
-    if default_user:
+    if default_user := app.config.get('T_DEFAULT_USER'):
         latest_tweets = tdb.search(keyword='*', user_screen_name=default_user, limit=10)
     else:
         latest_tweets = [tdb[tid] for tid in itertools.islice(reversed(tdb), 10)]
@@ -372,10 +360,8 @@ def index():
 
 
 @lru_cache(maxsize=1024)
-def fetch_tweet(tweet_id):
-
+def fetch_tweet(tweet_id: int | str) -> dict:
     token = app.config['T_TWITTER_TOKEN']
-
     resp = requests.get(
         'https://api.twitter.com/1.1/statuses/show.json',
         headers={
@@ -395,7 +381,6 @@ def fetch_tweet(tweet_id):
 
 @app.route('/tweet/<tweet_id>.<ext>')
 def get_tweet(tweet_id, ext):
-
     if ext not in ('txt', 'json', 'html'):
         flask.abort(404)
 
@@ -424,7 +409,7 @@ def get_tweet(tweet_id, ext):
 
     # HTML output
 
-    # Extract list images
+    # Extract media
     images = []
     videos = []
     try:
@@ -434,7 +419,7 @@ def get_tweet(tweet_id, ext):
         entities = tweet['entities']
     media = entities.get('media', [])
     for m in media:
-        # type = video
+        # type is video
         if m.get('type') == 'video':
             variants = m['video_info']['variants']
             hq_variant = max(variants, key=lambda v: v.get('bitrate', -1))
@@ -444,7 +429,7 @@ def get_tweet(tweet_id, ext):
             videos.append({
                 'url': media_url,
             })
-        # type = photo
+        # type is photo
         elif m.get('type') == 'photo':
             media_url = m['media_url_https']
             if not _is_external_tweet:
@@ -453,7 +438,7 @@ def get_tweet(tweet_id, ext):
                 'url': media_url,
                 'description': m.get('description', '')
             })
-        # type = unknown
+        # type is unknown
         else:
             pass
 
@@ -470,12 +455,12 @@ def get_tweet(tweet_id, ext):
 
 
 @app.route('/tweet/media/<path:fs_path>')
-def get_media_from_filesystem(fs_path):
+def get_media_from_filesystem(fs_path: str):
     return flask.send_from_directory(app.config['T_MEDIA_FS_PATH'], fs_path)
 
 
 @app.route('/tweet/search.<ext>')
-def search_tweet(ext):
+def search_tweet(ext: str):
     if ext not in ('html', 'txt', 'json'):
         flask.abort(404)
 
@@ -491,9 +476,8 @@ def search_tweet(ext):
     indexes = tdb.get_indexes()
 
     user = flask.request.args.get('u', '')
-    keyword = flask.request.args.get('q', '')
     index = flask.request.args.get('i', '')
-    if keyword:
+    if keyword := flask.request.args.get('q', ''):
         tweets = tdb.search(
             keyword=keyword,
             user_screen_name=user,