diff --git a/app/activitypub.py b/app/activitypub.py
index 11a1989..603e28a 100644
--- a/app/activitypub.py
+++ b/app/activitypub.py
@@ -10,6 +10,7 @@ from app import config
 from app.config import AP_CONTENT_TYPE  # noqa: F401
 from app.httpsig import auth
 from app.key import get_pubkey_as_pem
+from app.utils.url import check_url
 
 if TYPE_CHECKING:
     from app.actor import Actor
@@ -112,6 +113,8 @@ async def fetch(
     params: dict[str, Any] | None = None,
     disable_httpsig: bool = False,
 ) -> RawObject:
+    check_url(url)
+
     async with httpx.AsyncClient() as client:
         resp = await client.get(
             url,
@@ -291,6 +294,8 @@ def remove_context(raw_object: RawObject) -> RawObject:
 
 
 def post(url: str, payload: dict[str, Any]) -> httpx.Response:
+    check_url(url)
+
     resp = httpx.post(
         url,
         headers={
diff --git a/app/main.py b/app/main.py
index 9b6502d..cbdd7a3 100644
--- a/app/main.py
+++ b/app/main.py
@@ -66,6 +66,7 @@ from app.templates import is_current_user_admin
 from app.uploads import UPLOAD_DIR
 from app.utils import pagination
 from app.utils.emoji import EMOJIS_BY_NAME
+from app.utils.url import check_url
 from app.webfinger import get_remote_follow_template
 
 _RESIZED_CACHE: MutableMapping[tuple[str, int], tuple[bytes, str, Any]] = LFUCache(32)
@@ -76,15 +77,12 @@ _RESIZED_CACHE: MutableMapping[tuple[str, int], tuple[bytes, str, Any]] = LFUCac
 # Next:
 # - fix stream (only content from follows + mention, and dedup shares)
 # - custom emoji in data/
-# - handle remove activity
-# - retries httpx?
-# - DB models for webmentions
 # - allow to undo follow requests
 # - indieauth tweaks
 # - API for posting notes
 # - allow to block servers
 # - FT5 text search
-# - support update post with history
+# - support update post with history?
 #
 # - [ ] block support
 # - [ ] prevent SSRF (urlutils from little-boxes)
@@ -93,6 +91,12 @@ _RESIZED_CACHE: MutableMapping[tuple[str, int], tuple[bytes, str, Any]] = LFUCac
 
 
 class CustomMiddleware:
+    """Raw ASGI middleware as using starlette base middleware causes issues
+    with both:
+     - Jinja2: https://github.com/encode/starlette/issues/472
+     - async SQLAchemy: https://github.com/tiangolo/fastapi/issues/4719
+    """
+
     def __init__(
         self,
         app: ASGI3Application,
@@ -808,6 +812,8 @@ proxy_client = httpx.AsyncClient(follow_redirects=True, http2=True)
 async def serve_proxy_media(request: Request, encoded_url: str) -> StreamingResponse:
     # Decode the base64-encoded URL
     url = base64.urlsafe_b64decode(encoded_url).decode()
+    check_url(url)
+
     # Request the URL (and filter request headers)
     proxy_req = proxy_client.build_request(
         request.method,
@@ -856,6 +862,7 @@ async def serve_proxy_media_resized(
 
     # Decode the base64-encoded URL
     url = base64.urlsafe_b64decode(encoded_url).decode()
+    check_url(url)
 
     if cached_resp := _RESIZED_CACHE.get((url, size)):
         resized_content, resized_mimetype, resp_headers = cached_resp
diff --git a/app/outgoing_activities.py b/app/outgoing_activities.py
index e1e1d6e..a2a773e 100644
--- a/app/outgoing_activities.py
+++ b/app/outgoing_activities.py
@@ -22,6 +22,7 @@ from app.database import AsyncSession
 from app.database import SessionLocal
 from app.key import Key
 from app.utils.datetime import now
+from app.utils.url import check_url
 
 _MAX_RETRIES = 16
 
@@ -218,6 +219,7 @@ def process_next_outgoing_activity(db: Session) -> bool:
                 "target": next_activity.webmention_target,
             }
             logger.info(f"{webmention_payload=}")
+            check_url(next_activity.recipient)
             resp = httpx.post(
                 next_activity.recipient,
                 data=webmention_payload,
diff --git a/app/utils/url.py b/app/utils/url.py
index 16d97ab..352fc59 100644
--- a/app/utils/url.py
+++ b/app/utils/url.py
@@ -24,7 +24,7 @@ class InvalidURLError(Exception):
     pass
 
 
-@functools.lru_cache
+@functools.lru_cache(maxsize=256)
 def _getaddrinfo(hostname: str, port: int) -> str:
     try:
         ip_address = str(ipaddress.ip_address(hostname))
@@ -65,7 +65,7 @@ def is_url_valid(url: str) -> bool:
     return True
 
 
-def check_url(url: str, debug: bool = False) -> None:
+def check_url(url: str) -> None:
     logger.debug(f"check_url {url=}")
     if not is_url_valid(url):
         raise InvalidURLError(f'"{url}" is invalid')
diff --git a/app/utils/webmentions.py b/app/utils/webmentions.py
index 3f986d1..772d10e 100644
--- a/app/utils/webmentions.py
+++ b/app/utils/webmentions.py
@@ -8,6 +8,7 @@ from loguru import logger
 
 from app import config
 from app.utils.datetime import now
+from app.utils.url import check_url
 from app.utils.url import is_url_valid
 from app.utils.url import make_abs
 
@@ -46,6 +47,8 @@ async def discover_webmention_endpoint(url: str) -> str | None:
     Passes all the tests at https://webmention.rocks!
 
     """
+    check_url(url)
+
     wurl = await _discover_webmention_endoint(url)
     if wurl is None:
         return None
diff --git a/app/webfinger.py b/app/webfinger.py
index e6bb213..8daf9d0 100644
--- a/app/webfinger.py
+++ b/app/webfinger.py
@@ -5,6 +5,7 @@ import httpx
 from loguru import logger
 
 from app import config
+from app.utils.url import check_url
 
 
 async def webfinger(
@@ -32,6 +33,7 @@ async def webfinger(
         for i, proto in enumerate(protos):
             try:
                 url = f"{proto}://{host}/.well-known/webfinger"
+                check_url(url)
                 resp = await client.get(
                     url,
                     params={"resource": resource},