diff --git a/api_tests/run-federation-test.sh b/api_tests/run-federation-test.sh
index 3042fd344..aca57bc5f 100755
--- a/api_tests/run-federation-test.sh
+++ b/api_tests/run-federation-test.sh
@@ -2,6 +2,7 @@
 set -e
 
 export LEMMY_DATABASE_URL=postgres://lemmy:password@localhost:5432
+export LEMMY_TEST_FAST_FEDERATION=1 # by default, the persistent federation queue has delays in the scale of 30s-5min
 pushd ..
 cargo build
 rm target/lemmy_server || true
diff --git a/crates/federate/src/worker.rs b/crates/federate/src/worker.rs
index 3bc6218bb..b52e4dbbf 100644
--- a/crates/federate/src/worker.rs
+++ b/crates/federate/src/worker.rs
@@ -22,20 +22,47 @@ use std::{
 };
 use tokio::{sync::mpsc::UnboundedSender, time::sleep};
 use tokio_util::sync::CancellationToken;
-/// save state to db every n sends if there's no failures (otherwise state is saved after every attempt)
+
+/// Decrease the delays of the federation queue.
+/// Should only be used for federation tests since it significantly increases CPU and DB load of the federation queue.
+static LEMMY_TEST_FAST_FEDERATION: Lazy<bool> = Lazy::new(|| {
+  std::env::var("LEMMY_TEST_FAST_FEDERATION")
+    .map(|s| !s.is_empty())
+    .unwrap_or(false)
+});
+
+/// Check whether to save state to db every n sends if there's no failures (during failures state is saved after every attempt)
+/// This determines the batch size for loop_batch. After a batch ends and SAVE_STATE_EVERY_TIME has passed, the federation_queue_state is updated in the DB.
 static CHECK_SAVE_STATE_EVERY_IT: i64 = 100;
+/// Save state to db after this time has passed since the last state (so if the server crashes or is SIGKILLed, less than X seconds of activities are resent)
 static SAVE_STATE_EVERY_TIME: Duration = Duration::from_secs(60);
-/// recheck for new federation work every n seconds
-#[cfg(debug_assertions)]
-static WORK_FINISHED_RECHECK_DELAY: Duration = Duration::from_secs(1);
-#[cfg(not(debug_assertions))]
-static WORK_FINISHED_RECHECK_DELAY: Duration = Duration::from_secs(30);
-#[cfg(debug_assertions)]
-static FOLLOW_ADDITIONS_RECHECK_DELAY: Lazy<chrono::Duration> =
-  Lazy::new(|| chrono::Duration::minutes(1));
-#[cfg(not(debug_assertions))]
-static FOLLOW_ADDITIONS_RECHECK_DELAY: Lazy<chrono::Duration> =
-  Lazy::new(|| chrono::Duration::minutes(5));
+/// Recheck for new federation work every n seconds.
+///
+/// When the queue is processed faster than new activities are added and it reaches the current time with an empty batch,
+/// this is the delay the queue waits before it checks if new activities have been added to the sent_activities table.
+/// This delay is only applied if no federated activity happens during sending activities of the last batch.
+static WORK_FINISHED_RECHECK_DELAY: Lazy<Duration> = Lazy::new(|| {
+  if *LEMMY_TEST_FAST_FEDERATION {
+    Duration::from_secs(1)
+  } else {
+    Duration::from_secs(30)
+  }
+});
+/// interval with which new additions to community_followers are queried.
+///
+/// The first time some user on an instance follows a specific remote community (or, more precisely: the first time a (followed_community_id, follower_inbox_url) tuple appears),
+/// this delay limits the maximum time until the follow actually results in activities from that community id being sent to that inbox url.
+/// This delay currently needs to not be too small because the DB load is currently fairly high because of the current structure of storing inboxes for every person, not having a separate list of shared_inboxes, and the architecture of having every instance queue be fully separate.
+/// (see https://github.com/LemmyNet/lemmy/issues/3958)
+static FOLLOW_ADDITIONS_RECHECK_DELAY: Lazy<chrono::Duration> = Lazy::new(|| {
+  if *LEMMY_TEST_FAST_FEDERATION {
+    chrono::Duration::seconds(1)
+  } else {
+    chrono::Duration::minutes(2)
+  }
+});
+/// The same as FOLLOW_ADDITIONS_RECHECK_DELAY, but triggering when the last person on an instance unfollows a specific remote community.
+/// This is expected to happen pretty rarely and updating it in a timely manner is not too important.
 static FOLLOW_REMOVALS_RECHECK_DELAY: Lazy<chrono::Duration> =
   Lazy::new(|| chrono::Duration::hours(1));
 pub(crate) struct InstanceWorker {
@@ -121,6 +148,7 @@ impl InstanceWorker {
     }
     Ok(())
   }
+  /// send out a batch of CHECK_SAVE_STATE_EVERY_IT activities
   async fn loop_batch(&mut self, pool: &mut DbPool<'_>) -> Result<()> {
     let latest_id = get_latest_activity_id(pool).await?;
     if self.state.last_successful_id == -1 {
@@ -134,7 +162,7 @@ impl InstanceWorker {
     if id == latest_id {
       // no more work to be done, wait before rechecking
       tokio::select! {
-        () = sleep(WORK_FINISHED_RECHECK_DELAY) => {},
+        () = sleep(*WORK_FINISHED_RECHECK_DELAY) => {},
         () = self.stop.cancelled() => {}
       }
       return Ok(());