diff --git a/src/server/features/keywords/services/research/refresh-metrics.ts b/src/server/features/keywords/services/research/refresh-metrics.ts
index 7214f6c..3182200 100644
--- a/src/server/features/keywords/services/research/refresh-metrics.ts
+++ b/src/server/features/keywords/services/research/refresh-metrics.ts
@@ -7,6 +7,11 @@ import {
 import type { BillingCustomerContext } from "@/server/billing/subscription";
 import type { RefreshSavedKeywordMetricsInput } from "@/types/schemas/keywords";
 
+// Cap concurrent D1 upserts per group. A project can accumulate thousands of
+// saved keywords in one location/language, and fanning out one promise each
+// would flood D1/Worker resources; write in bounded chunks instead.
+const REFRESH_UPSERT_BATCH_SIZE = 100;
+
 export async function refreshSavedKeywordMetrics(
   input: RefreshSavedKeywordMetricsInput,
   billingCustomer: BillingCustomerContext,
@@ -41,24 +46,27 @@ export async function refreshSavedKeywordMetrics(
       metrics.map((metric) => [metric.keyword.toLowerCase(), metric]),
     );
 
-    await Promise.all(
-      groupRows.map((r) => {
-        const metric = byKeyword.get(r.row.keyword.toLowerCase());
-        if (!metric) return Promise.resolve();
-        return KeywordResearchRepository.upsertKeywordMetric({
-          projectId: input.projectId,
-          keyword: r.row.keyword,
-          locationCode,
-          languageCode,
-          searchVolume: metric.searchVolume,
-          cpc: metric.cpc,
-          competition: metric.competition,
-          keywordDifficulty: metric.keywordDifficulty,
-          intent: normalizeIntent(metric.intent),
-          monthlySearchesJson: JSON.stringify(metric.monthlySearches),
-        });
-      }),
-    );
+    for (let i = 0; i < groupRows.length; i += REFRESH_UPSERT_BATCH_SIZE) {
+      const chunk = groupRows.slice(i, i + REFRESH_UPSERT_BATCH_SIZE);
+      await Promise.all(
+        chunk.map((r) => {
+          const metric = byKeyword.get(r.row.keyword.toLowerCase());
+          if (!metric) return Promise.resolve();
+          return KeywordResearchRepository.upsertKeywordMetric({
+            projectId: input.projectId,
+            keyword: r.row.keyword,
+            locationCode,
+            languageCode,
+            searchVolume: metric.searchVolume,
+            cpc: metric.cpc,
+            competition: metric.competition,
+            keywordDifficulty: metric.keywordDifficulty,
+            intent: normalizeIntent(metric.intent),
+            monthlySearchesJson: JSON.stringify(metric.monthlySearches),
+          });
+        }),
+      );
+    }
 
     updated += byKeyword.size;
   }