diff --git a/lib/auth.js b/lib/auth.js
index b3895d6..1c502b4 100644
--- a/lib/auth.js
+++ b/lib/auth.js
@@ -2,8 +2,6 @@ const fs = require('fs');
 const path = require('path');
 const {google} = require('googleapis');
 const {applyRateLimitBuffer} = require('./rate');
-const pThrottleModule = require('p-throttle');
-const pThrottle = pThrottleModule.default || pThrottleModule;
 
 function loadApiKeys(config) {
   const apiKeys = [];
@@ -58,7 +56,9 @@ function loadServiceAccounts(config) {
 function createServiceAccountBatchFetcher(config) {
   const accounts = loadServiceAccounts(config);
   if (accounts.length === 0) return null;
-
+  // Build raw fetchers and track next available timestamps to allow
+  // selecting a credential whose slot is available now. If none are
+  // immediately available, wait the minimum required time.
   const fetchers = accounts.map(({path: credentialsPath, rateLimitPerMinute}) => {
     const resolvedPath = path.isAbsolute(credentialsPath) ? credentialsPath : path.resolve(process.cwd(), credentialsPath);
     if (!fs.existsSync(resolvedPath)) {
@@ -82,7 +82,8 @@ function createServiceAccountBatchFetcher(config) {
 
     const bufferedRateLimit = applyRateLimitBuffer(rateLimitPerMinute);
     const interval = Math.ceil(60000 / bufferedRateLimit);
-    const throttled = pThrottle({limit: 1, interval})(async (documentId, sheetNames) => {
+
+    const fetchRaw = async (documentId, sheetNames) => {
       const sheets = google.sheets({version: 'v4', auth: authClient});
       const request = {spreadsheetId: documentId, ranges: sheetNames};
       const response = await sheets.spreadsheets.values.batchGet(request);
@@ -93,16 +94,47 @@ function createServiceAccountBatchFetcher(config) {
         rowsBySheet[sheetName] = valueRanges[i]?.values || [];
       }
       return rowsBySheet;
-    });
+    };
 
-    return {authClient, fetch: throttled};
+    return {authClient, fetchRaw, interval, nextAvailable: 0};
   });
 
   let currentIndex = 0;
+
+  const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
+
   return async (documentId, sheetNames) => {
-    const worker = fetchers[currentIndex];
-    currentIndex = (currentIndex + 1) % fetchers.length;
-    return worker.fetch(documentId, sheetNames);
+    const now = () => Date.now();
+
+    // Try to find an available worker without blocking; check each worker once
+    for (let i = 0; i < fetchers.length; i += 1) {
+      const idx = (currentIndex + i) % fetchers.length;
+      const worker = fetchers[idx];
+      if (now() >= worker.nextAvailable) {
+        currentIndex = (idx + 1) % fetchers.length;
+        worker.nextAvailable = now() + worker.interval;
+        return worker.fetchRaw(documentId, sheetNames);
+      }
+    }
+
+    // If none available immediately, pick the earliest one and wait until it's free
+    let earliestIdx = 0;
+    let earliestTime = fetchers[0].nextAvailable;
+    for (let i = 1; i < fetchers.length; i += 1) {
+      if (fetchers[i].nextAvailable < earliestTime) {
+        earliestTime = fetchers[i].nextAvailable;
+        earliestIdx = i;
+      }
+    }
+
+    const waitMs = Math.max(0, earliestTime - now());
+    if (waitMs > 0) await sleep(waitMs);
+
+    // After waiting, reserve the slot and call
+    const worker = fetchers[earliestIdx];
+    currentIndex = (earliestIdx + 1) % fetchers.length;
+    worker.nextAvailable = now() + worker.interval;
+    return worker.fetchRaw(documentId, sheetNames);
   };
 }
 
@@ -111,11 +143,11 @@ function createApiKeyBatchFetcher(config) {
   if (apiKeys.length === 0) {
     return null;
   }
-
   const fetchers = apiKeys.map(({key, rateLimitPerMinute}) => {
     const bufferedRateLimit = applyRateLimitBuffer(rateLimitPerMinute);
     const interval = Math.ceil(60000 / bufferedRateLimit);
-    const throttled = pThrottle({limit: 1, interval})(async (documentId, sheetNames) => {
+
+    const fetchRaw = async (documentId, sheetNames) => {
       const sheets = google.sheets({version: 'v4'});
       const request = {spreadsheetId: documentId, ranges: sheetNames, key};
       const response = await sheets.spreadsheets.values.batchGet(request);
@@ -126,15 +158,44 @@ function createApiKeyBatchFetcher(config) {
         rowsBySheet[sheetName] = valueRanges[i]?.values || [];
       }
       return rowsBySheet;
-    });
-    return {key, fetch: throttled};
+    };
+
+    return {key, fetchRaw, interval, nextAvailable: 0};
   });
 
   let currentIndex = 0;
+
+  const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));
+
   return async (documentId, sheetNames) => {
-    const worker = fetchers[currentIndex];
-    currentIndex = (currentIndex + 1) % fetchers.length;
-    return worker.fetch(documentId, sheetNames);
+    const now = () => Date.now();
+
+    for (let i = 0; i < fetchers.length; i += 1) {
+      const idx = (currentIndex + i) % fetchers.length;
+      const worker = fetchers[idx];
+      if (now() >= worker.nextAvailable) {
+        currentIndex = (idx + 1) % fetchers.length;
+        worker.nextAvailable = now() + worker.interval;
+        return worker.fetchRaw(documentId, sheetNames);
+      }
+    }
+
+    let earliestIdx = 0;
+    let earliestTime = fetchers[0].nextAvailable;
+    for (let i = 1; i < fetchers.length; i += 1) {
+      if (fetchers[i].nextAvailable < earliestTime) {
+        earliestTime = fetchers[i].nextAvailable;
+        earliestIdx = i;
+      }
+    }
+
+    const waitMs = Math.max(0, earliestTime - now());
+    if (waitMs > 0) await sleep(waitMs);
+
+    const worker = fetchers[earliestIdx];
+    currentIndex = (earliestIdx + 1) % fetchers.length;
+    worker.nextAvailable = now() + worker.interval;
+    return worker.fetchRaw(documentId, sheetNames);
   };
 }