diff --git a/packages/core/src/submodules/protocols/json/AwsJson1_1Protocol.spec.ts b/packages/core/src/submodules/protocols/json/AwsJson1_1Protocol.spec.ts
index 1ab24ff49fa8..7714fa4d425e 100644
--- a/packages/core/src/submodules/protocols/json/AwsJson1_1Protocol.spec.ts
+++ b/packages/core/src/submodules/protocols/json/AwsJson1_1Protocol.spec.ts
@@ -1,7 +1,7 @@
 import { HttpResponse } from "@smithy/protocol-http";
 import { describe, expect, test as it } from "vitest";
 
-import { context, deleteObjects } from "../test-schema.spec";
+import { context, createNestingWidget, deleteObjects, nestingWidget } from "../test-schema.spec";
 import { AwsJson1_1Protocol } from "./AwsJson1_1Protocol";
 
 /**
@@ -122,4 +122,55 @@ describe(AwsJson1_1Protocol, () => {
       },
     });
   });
+
+  describe("performance baseline", () => {
+    const protocol = new AwsJson1_1Protocol({
+      defaultNamespace: "",
+      serviceTarget: "JsonRpc11",
+    });
+
+    it("should serialize objects", async () => {
+      const timings: string[] = [];
+      const objects = [];
+
+      for (let i = 0; i < 12; ++i) {
+        const o = createNestingWidget(2 ** i);
+        objects.push(o);
+      }
+
+      for (let i = 0; i < objects.length; ++i) {
+        const o = objects[i];
+
+        const A = performance.now();
+        const request = await protocol.serializeRequest(
+          {
+            input: nestingWidget,
+            output: "unit",
+            traits: 0,
+            namespace: "operation",
+            name: "ns",
+          },
+          o,
+          context
+        );
+        const B = performance.now();
+
+        timings.push(
+          `${(B - A).toFixed(2)}ms (JSON length = ${request.body.length}, ${
+            request.body.length / 1024 / (B - A)
+          } kb/ms)`
+        );
+      }
+
+      /**
+       * No assertion here.
+       * In the initial dual-pass implementation,
+       * par time is 0 to 30ms for up to 288899 chars of JSON. Up to 11 kb/ms. (kuhe's computer)
+       *
+       * In the single-pass implementation using string buildup,
+       * par time is 0 to 51ms for up to 288899 chars of JSON. Up to 13 kb/ms. (kuhe's computer)
+       */
+      console.log(`${protocol.constructor.name} performance timings`, timings);
+    });
+  });
 });