diff --git a/betty/app/__init__.py b/betty/app/__init__.py
index 9a59cea7e..098bd2752 100644
--- a/betty/app/__init__.py
+++ b/betty/app/__init__.py
@@ -3,7 +3,6 @@
 from __future__ import annotations
 
 import operator
-import os as stdos
 import weakref
 from collections.abc import Callable
 from contextlib import suppress
@@ -341,17 +340,6 @@ def renderer(self) -> Renderer:
     def renderer(self) -> None:
         self._renderer = None
 
-    @property
-    def concurrency(self) -> int:
-        with suppress(KeyError):
-            return int(stdos.environ['BETTY_CONCURRENCY'])
-        # Assume that any machine that runs Betty has at least two CPU cores.
-        return stdos.cpu_count() or 2
-
-    @property
-    def async_concurrency(self) -> int:
-        return self.concurrency ** 2
-
     @property
     def http_client(self) -> aiohttp.ClientSession:
         if not self._http_client:
diff --git a/betty/generate.py b/betty/generate.py
index 0797bd36c..2a451488b 100644
--- a/betty/generate.py
+++ b/betty/generate.py
@@ -22,7 +22,7 @@
 from aiofiles.threadpool.text import AsyncTextIOWrapper
 
 from betty.app import App
-from betty.asyncio import sync, gather
+from betty.asyncio import sync
 from betty.json.linked_data import LinkedDataDumpable
 from betty.json.schema import Schema
 from betty.locale import get_display_name
@@ -36,6 +36,9 @@
 _GenerationWorkerPoolTaskP = ParamSpec('_GenerationWorkerPoolTaskP')
 
 
+_THREAD_CONCURRENCY = 16
+
+
 def getLogger() -> logging.Logger:
     """
     Get the site generation logger.
@@ -84,13 +87,12 @@ def __init__(self, app: App, task_context: GenerationContext):
         self._workers: list[Future[None]] = []
 
     async def __aenter__(self) -> Self:
-        self._executor = ThreadPoolExecutor(max_workers=self._app.concurrency)
-        for _ in range(0, self._app.concurrency):
+        self._executor = ThreadPoolExecutor(max_workers=_THREAD_CONCURRENCY)
+        for _ in range(0, _THREAD_CONCURRENCY):
             self._workers.append(self._executor.submit(_GenerationPoolWorker(
                 self._queue,
                 self._cancel,
                 self._finish,
-                self._app.concurrency,
                 self._task_context,
             )))
         return self
@@ -125,23 +127,15 @@ def __init__(
         task_queue: queue.Queue[_GenerationQueueItem],
         cancel: threading.Event,
         finish: threading.Event,
-        async_concurrency: int,
         task_context: GenerationContext,
     ):
         self._task_queue = task_queue
         self._cancel = cancel
         self._finish = finish
-        self._async_concurrency = async_concurrency
         self._context = task_context
 
     @sync
     async def __call__(self) -> None:
-        await gather(*(
-            self._perform_tasks()
-            for _ in range(0, self._async_concurrency)
-        ))
-
-    async def _perform_tasks(self) -> None:
         while not self._cancel.is_set():
             try:
                 item = self._task_queue.get_nowait()