diff --git a/lib/autoPipelining.ts b/lib/autoPipelining.ts
index 238fe1149..e2fbfdecd 100644
--- a/lib/autoPipelining.ts
+++ b/lib/autoPipelining.ts
@@ -1,4 +1,5 @@
 import * as PromiseContainer from "./promiseContainer";
+import { flatten, isArguments } from "./utils/lodash";
 import * as calculateSlot from "cluster-key-slot";
 import asCallback from "standard-as-callback";
 
@@ -74,11 +75,35 @@ export function shouldUseAutoPipelining(
   );
 }
 
+/**
+ * @private
+ */
+export function getFirstValueInFlattenedArray(
+  args: (string | string[])[]
+): string | undefined {
+  for (let i = 0; i < args.length; i++) {
+    const arg = args[i];
+    if (typeof arg === "string") {
+      return arg;
+    } else if (Array.isArray(arg) || isArguments(arg)) {
+      if (arg.length === 0) {
+        continue;
+      }
+      return arg[0];
+    }
+    const flattened = flatten([arg]);
+    if (flattened.length > 0) {
+      return flattened[0];
+    }
+  }
+  return undefined;
+}
+
 export function executeWithAutoPipelining(
   client,
   functionName: string,
   commandName: string,
-  args: string[],
+  args: (string | string[])[],
   callback
 ) {
   const CustomPromise = PromiseContainer.get();
@@ -104,7 +129,16 @@ export function executeWithAutoPipelining(
   }
 
   // If we have slot information, we can improve routing by grouping slots served by the same subset of nodes
-  const slotKey = client.isCluster ? client.slots[calculateSlot(args[0])].join(",") : 'main';
+  // Note that the first value in args may be a (possibly empty) array.
+  // ioredis will only flatten one level of the array, in the Command constructor.
+  const prefix = client.options.keyPrefix || "";
+  const slotKey = client.isCluster
+    ? client.slots[
+        calculateSlot(
+          `${client.options.keyPrefix}${getFirstValueInFlattenedArray(args)}`
+        )
+      ].join(",")
+    : "main";
 
   if (!client._autoPipelines.has(slotKey)) {
     const pipeline = client.pipeline();
diff --git a/lib/utils/lodash.ts b/lib/utils/lodash.ts
index c903fdc59..ec1a26b91 100644
--- a/lib/utils/lodash.ts
+++ b/lib/utils/lodash.ts
@@ -1,6 +1,7 @@
 import defaults = require("lodash.defaults");
 import flatten = require("lodash.flatten");
+import isArguments = require("lodash.isarguments");
 
 export function noop() {}
 
-export { defaults, flatten };
+export { defaults, flatten, isArguments };
diff --git a/package-lock.json b/package-lock.json
index 7b855eef0..86c806371 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -288,6 +288,15 @@
         "@types/lodash": "*"
       }
     },
+    "@types/lodash.isarguments": {
+      "version": "3.1.6",
+      "resolved": "http://artifactory.amz.mtmemgmt.com/artifactory/api/npm/npm-tmg-local/@types/lodash.isarguments/-/lodash.isarguments-3.1.6.tgz",
+      "integrity": "sha1-WgEtFkZs3Q6hg/U9/CZErcodi4g=",
+      "dev": true,
+      "requires": {
+        "@types/lodash": "*"
+      }
+    },
     "@types/minimatch": {
       "version": "3.0.3",
       "resolved": "https://registry.npmjs.org/@types/minimatch/-/minimatch-3.0.3.tgz",
@@ -2671,6 +2680,11 @@
       "integrity": "sha1-LRd/ZS+jHpObRDjVNBSZ36OCXpk=",
       "dev": true
     },
+    "lodash.isarguments": {
+      "version": "3.1.0",
+      "resolved": "http://artifactory.amz.mtmemgmt.com/artifactory/api/npm/npm-tmg-local/lodash.isarguments/-/lodash.isarguments-3.1.0.tgz",
+      "integrity": "sha1-L1c9hcaiQon/AGY7SRwdM4/zRYo="
+    },
     "lodash.map": {
       "version": "4.6.0",
       "resolved": "https://registry.npmjs.org/lodash.map/-/lodash.map-4.6.0.tgz",
diff --git a/package.json b/package.json
index 283391896..fa844719f 100644
--- a/package.json
+++ b/package.json
@@ -38,6 +38,7 @@
     "denque": "^1.1.0",
     "lodash.defaults": "^4.2.0",
     "lodash.flatten": "^4.4.0",
+    "lodash.isarguments": "^3.1.0",
     "p-map": "^2.1.0",
     "redis-commands": "1.7.0",
     "redis-errors": "^1.2.0",
@@ -53,6 +54,7 @@
     "@types/debug": "^4.1.5",
     "@types/lodash.defaults": "^4.2.6",
     "@types/lodash.flatten": "^4.4.6",
+    "@types/lodash.isarguments": "^3.1.6",
     "@types/mocha": "^7.0.2",
     "@types/node": "^13.11.0",
     "@types/redis-errors": "1.2.0",
diff --git a/test/functional/cluster/autopipelining.ts b/test/functional/cluster/autopipelining.ts
index 02f933d64..82ac77add 100644
--- a/test/functional/cluster/autopipelining.ts
+++ b/test/functional/cluster/autopipelining.ts
@@ -35,6 +35,10 @@ describe("autoPipelining for cluster", function () {
       if (argv[0] === "get" && argv[1] === "foo6") {
         return "bar6";
       }
+
+      if (argv[0] === "get" && argv[1] === "baz:foo10") {
+        return "bar10";
+      }
     });
 
     new MockServer(30002, function (argv) {
@@ -68,6 +72,10 @@ describe("autoPipelining for cluster", function () {
         return "bar5";
       }
 
+      if (argv[0] === "get" && argv[1] === "baz:foo1") {
+        return "bar1";
+      }
+
       if (argv[0] === "evalsha") {
         return argv.slice(argv.length - 4);
       }
@@ -177,6 +185,40 @@ describe("autoPipelining for cluster", function () {
     cluster.disconnect();
   });
 
+  it("should support building pipelines when a prefix is used", async () => {
+    const cluster = new Cluster(hosts, {
+      enableAutoPipelining: true,
+      keyPrefix: "baz:",
+    });
+    await new Promise((resolve) => cluster.once("connect", resolve));
+
+    await cluster.set("foo1", "bar1");
+    await cluster.set("foo10", "bar10");
+
+    expect(
+      await Promise.all([cluster.get("foo1"), cluster.get("foo10")])
+    ).to.eql(["bar1", "bar10"]);
+
+    cluster.disconnect();
+  });
+
+  it("should support building pipelines when a prefix is used with arrays to flatten", async () => {
+    const cluster = new Cluster(hosts, {
+      enableAutoPipelining: true,
+      keyPrefix: "baz:",
+    });
+    await new Promise((resolve) => cluster.once("connect", resolve));
+
+    await cluster.set(["foo1"], "bar1");
+    await cluster.set(["foo10"], "bar10");
+
+    expect(
+      await Promise.all([cluster.get(["foo1"]), cluster.get(["foo10"])])
+    ).to.eql(["bar1", "bar10"]);
+
+    cluster.disconnect();
+  });
+
   it("should support commands queued after a pipeline is already queued for execution", (done) => {
     const cluster = new Cluster(hosts, { enableAutoPipelining: true });
 
@@ -407,9 +449,9 @@ describe("autoPipelining for cluster", function () {
     const promise4 = cluster.set("foo6", "bar");
 
     // Override slots to induce a failure
-    const key1Slot = calculateKeySlot('foo1');
-    const key2Slot = calculateKeySlot('foo2');
-    const key5Slot = calculateKeySlot('foo5');
+    const key1Slot = calculateKeySlot("foo1");
+    const key2Slot = calculateKeySlot("foo2");
+    const key5Slot = calculateKeySlot("foo5");
 
     changeSlot(cluster, key1Slot, key2Slot);
     changeSlot(cluster, key2Slot, key5Slot);
@@ -498,9 +540,9 @@ describe("autoPipelining for cluster", function () {
       expect(cluster.autoPipelineQueueSize).to.eql(4);
 
       // Override slots to induce a failure
-      const key1Slot = calculateKeySlot('foo1');
-      const key2Slot = calculateKeySlot('foo2');
-      const key5Slot = calculateKeySlot('foo5');
+      const key1Slot = calculateKeySlot("foo1");
+      const key2Slot = calculateKeySlot("foo2");
+      const key5Slot = calculateKeySlot("foo5");
       changeSlot(cluster, key1Slot, key2Slot);
       changeSlot(cluster, key2Slot, key5Slot);
     });
@@ -547,8 +589,8 @@ describe("autoPipelining for cluster", function () {
 
       expect(cluster.autoPipelineQueueSize).to.eql(3);
 
-      const key1Slot = calculateKeySlot('foo1');
-      const key2Slot = calculateKeySlot('foo2');
+      const key1Slot = calculateKeySlot("foo1");
+      const key2Slot = calculateKeySlot("foo2");
       changeSlot(cluster, key1Slot, key2Slot);
     });
   });
diff --git a/test/unit/autoPipelining.ts b/test/unit/autoPipelining.ts
new file mode 100644
index 000000000..f8cc053b0
--- /dev/null
+++ b/test/unit/autoPipelining.ts
@@ -0,0 +1,38 @@
+import { expect } from "chai";
+import { getFirstValueInFlattenedArray } from "../../lib/autoPipelining";
+import { flatten } from "../../lib/utils/lodash";
+
+describe("autoPipelining", function () {
+  const expectGetFirstValueIs = (values, expected) => {
+    expect(getFirstValueInFlattenedArray(values)).to.eql(expected);
+    // getFirstValueInFlattenedArray should behave the same way as flatten(args)[0]
+    // but be much more efficient.
+    expect(flatten(values)[0]).to.eql(expected);
+  };
+
+  it("should be able to efficiently get array args", function () {
+    expectGetFirstValueIs([], undefined);
+    expectGetFirstValueIs([null, "key"], null);
+    expectGetFirstValueIs(["key", "value"], "key");
+    expectGetFirstValueIs([[], "key"], "key");
+    expectGetFirstValueIs([["key"]], "key");
+    // @ts-ignore
+    expectGetFirstValueIs([[["key"]]], ["key"]);
+    // @ts-ignore
+    expectGetFirstValueIs([0, 1, 2, 3, 4], 0);
+    // @ts-ignore
+    expectGetFirstValueIs([[true]], true);
+    // @ts-ignore
+    expectGetFirstValueIs([Buffer.from("test")], Buffer.from("test"));
+    // @ts-ignore
+    expectGetFirstValueIs([{}], {});
+    // lodash.isArguments is true for this legacy js way to get argument lists
+    const createArguments = function () {
+      return arguments;
+    };
+    // @ts-ignore
+    expectGetFirstValueIs([createArguments(), createArguments("key")], "key");
+    // @ts-ignore
+    expectGetFirstValueIs([createArguments("")], "");
+  });
+});