diff --git a/src/clustering.js b/src/clustering.js
index 875d5f9..a8acd11 100644
--- a/src/clustering.js
+++ b/src/clustering.js
@@ -92,6 +92,8 @@ async function backfillMissingClusters(limit = 128) {
 
       assignEvent.run(eventId, article.id);
       processed++;
+
+      await new Promise((resolve) => setImmediate(resolve));
     }
   } finally {
     clusteringRunning = false;