diff --git a/backend/server.js b/backend/server.js
index ead40e6..57f5d4e 100644
--- a/backend/server.js
+++ b/backend/server.js
@@ -13,6 +13,8 @@ const port = 3001;
 app.use(cors());
 app.use(express.json());
 app.use(compression());
+// Disable Express auto-ETag to avoid weak ETags on JSON bodies
+app.set('etag', false);
 
 // Expose important headers to browser JS (for CORS)
 app.use((req, res, next) => {
@@ -27,9 +29,13 @@ app.use(express.static(path.join(__dirname, 'public')));
 const s3 = new AWS.S3({
     endpoint: 'https://storage.yandexcloud.net',
     region: process.env.AWS_REGION,
+    s3ForcePathStyle: true,
+    signatureVersion: 'v4',
+    httpOptions: { timeout: 15000 },
+    maxRetries: 3,
     credentials: {
-        accessKeyId: process.env.AWS_ACCESS_KEY_ID,
-        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
+        accessKeyId: process.env.AWS_ACCESS_KEY_ID || process.env.S3_ACCESS_KEY_ID,
+        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY || process.env.S3_SECRET_ACCESS_KEY,
     }
 });
 
@@ -365,11 +371,10 @@ app.post('/api/asns', async (req, res) => {
         if (!validateAsns(asns || [])) {
             return res.status(400).json({ message: 'Invalid payload format for asns' });
         }
-        if (etag) {
-            const current = await headS3ObjectEtag('bgp_data/asns.txt').catch(() => undefined);
-            if (current && current.replace(/\"/g, '"') !== String(etag)) {
-                return res.status(412).json({ message: 'Precondition Failed: ETag mismatch' });
-            }
+        let current = null;
+        try { current = await headS3ObjectEtag('bgp_data/asns.txt'); } catch {}
+        if (current && etag && current !== String(etag)) {
+            return res.status(412).json({ message: 'Precondition Failed: ETag mismatch', currentEtag: current });
         }
     } catch {}
 
@@ -388,7 +393,7 @@ app.post('/api/asns', async (req, res) => {
             if (head.LastModified) res.set('Last-Modified', new Date(head.LastModified).toUTCString());
             if (typeof head.ContentLength === 'number') res.set('Content-Length-Source', String(head.ContentLength));
         } catch {}
-        res.send('File updated successfully');
+        res.json({ ok: true });
     } catch (error) {
         console.error(error);
         res.status(500).send('Error writing to S3');
@@ -453,11 +458,10 @@ app.post('/api/domains-new', async (req, res) => {
         if (!validateDomainsNew(domains || [])) {
             return res.status(400).json({ message: 'Invalid payload format for domains-new' });
         }
-        if (etag) {
-            const current = await headS3ObjectEtag('bgp_data/domains_community.txt').catch(() => undefined);
-            if (current && current.replace(/\"/g, '"') !== String(etag)) {
-                return res.status(412).json({ message: 'Precondition Failed: ETag mismatch' });
-            }
+        let current = null;
+        try { current = await headS3ObjectEtag('bgp_data/domains_community.txt'); } catch {}
+        if (current && etag && current !== String(etag)) {
+            return res.status(412).json({ message: 'Precondition Failed: ETag mismatch', currentEtag: current });
         }
     } catch {}
 
@@ -476,7 +480,7 @@ app.post('/api/domains-new', async (req, res) => {
             if (head.LastModified) res.set('Last-Modified', new Date(head.LastModified).toUTCString());
             if (typeof head.ContentLength === 'number') res.set('Content-Length-Source', String(head.ContentLength));
         } catch {}
-        res.send('File updated successfully');
+        res.json({ ok: true });
     } catch (error) {
         console.error(error);
         res.status(500).send('Error writing to S3');
@@ -541,11 +545,10 @@ app.post('/api/ip-ranges', async (req, res) => {
         if (!validateIpRanges(ipRanges || [])) {
             return res.status(400).json({ message: 'Invalid payload format for ip-ranges' });
         }
-        if (etag) {
-            const current = await headS3ObjectEtag('bgp_data/ips.txt').catch(() => undefined);
-            if (current && current.replace(/\"/g, '"') !== String(etag)) {
-                return res.status(412).json({ message: 'Precondition Failed: ETag mismatch' });
-            }
+        let current = null;
+        try { current = await headS3ObjectEtag('bgp_data/ips.txt'); } catch {}
+        if (current && etag && current !== String(etag)) {
+            return res.status(412).json({ message: 'Precondition Failed: ETag mismatch', currentEtag: current });
         }
     } catch {}
 
@@ -564,7 +567,7 @@ app.post('/api/ip-ranges', async (req, res) => {
             if (head.LastModified) res.set('Last-Modified', new Date(head.LastModified).toUTCString());
             if (typeof head.ContentLength === 'number') res.set('Content-Length-Source', String(head.ContentLength));
         } catch {}
-        res.send('File updated successfully');
+        res.json({ ok: true });
     } catch (error) {
         console.error(error);
         res.status(500).send('Error writing to S3');