diff --git a/packages/db/src/buffers/session-buffer.ts b/packages/db/src/buffers/session-buffer.ts
index 0fc221ad..701ee81c 100644
--- a/packages/db/src/buffers/session-buffer.ts
+++ b/packages/db/src/buffers/session-buffer.ts
@@ -191,14 +191,23 @@ export class SessionBuffer extends BaseBuffer {
 
       if (events.length === 0) return;
 
-      const sessions = events.map((e) => getSafeJson<IClickhouseSession>(e));
+      const sessions = events
+        .map((e) => getSafeJson<IClickhouseSession>(e))
+        .map((session) => {
+          return {
+            ...session,
+            duration: Math.max(0, session?.duration || 0),
+          };
+        });
 
-      // Insert to ClickHouse
-      await ch.insert({
-        table: TABLE_NAMES.sessions,
-        values: sessions,
-        format: 'JSONEachRow',
-      });
+      for (const chunk of this.chunks(sessions, 1000)) {
+        // Insert to ClickHouse
+        await ch.insert({
+          table: TABLE_NAMES.sessions,
+          values: chunk,
+          format: 'JSONEachRow',
+        });
+      }
 
       // Only remove events after successful insert
       await this.redis.ltrim(this.redisKey, events.length, -1);