diff --git a/eslint.config.js b/eslint.config.js
index c0090f571..4197ace1c 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -72,6 +72,10 @@ const performanceConcerns = [
     selector: "ImportDeclaration[source.value=/package.json$/]", // #2974
     message: "it can not be tree shaken, use tsdown and process.env instead",
   },
+  {
+    selector: "CallExpression[callee.property.name=/^(shift|unshift)$/]", // #3343
+    message: "shifting is 2-20x slower than index-based iteration",
+  },
 ];
 
 const tsFactoryConcerns = [
diff --git a/express-zod-api/bench/can-merge.bench.ts b/express-zod-api/bench/can-merge.bench.ts
deleted file mode 100644
index 0a81069b0..000000000
--- a/express-zod-api/bench/can-merge.bench.ts
+++ /dev/null
@@ -1,64 +0,0 @@
-import { bench, describe } from "vitest";
-import * as R from "ramda";
-
-const mergeableKeys = new Set([
-  "type",
-  "properties",
-  "required",
-  "examples",
-  "description",
-  "additionalProperties",
-]);
-
-const current = (subject: Record<string, unknown>) =>
-  R.pipe(
-    Object.keys,
-    R.without([
-      "type",
-      "properties",
-      "required",
-      "examples",
-      "description",
-      "additionalProperties",
-    ] as string[]),
-    R.isEmpty,
-  )(subject);
-
-const featured = (subject: Record<string, unknown>): boolean => {
-  for (const key of Object.keys(subject))
-    if (!mergeableKeys.has(key)) return false;
-  return true;
-};
-
-describe.each([
-  {},
-  { type: "object" },
-  { type: "object", properties: {} },
-  { type: "object", properties: {}, required: [] },
-  { type: "object", properties: {}, required: [], examples: [] },
-  {
-    type: "object",
-    properties: {},
-    required: [],
-    examples: [],
-    description: "test",
-  },
-  {
-    type: "object",
-    properties: {},
-    required: [],
-    examples: [],
-    description: "test",
-    additionalProperties: false,
-  },
-  { type: "object", title: "test" },
-  { type: "object", format: "date-time", title: "test" },
-])("Experiment for canMerge %#", (subject) => {
-  bench(`current`, () => {
-    current(subject);
-  });
-
-  bench(`featured`, () => {
-    featured(subject);
-  });
-});
diff --git a/express-zod-api/bench/queue-ops.bench.ts b/express-zod-api/bench/queue-ops.bench.ts
new file mode 100644
index 000000000..80bf84c46
--- /dev/null
+++ b/express-zod-api/bench/queue-ops.bench.ts
@@ -0,0 +1,42 @@
+import { bench, describe } from "vitest";
+
+const smallQueue = Array.from({ length: 5 }, (_, i) => ({
+  id: i,
+  data: `item-${i}`,
+}));
+const mediumQueue = Array.from({ length: 20 }, (_, i) => ({
+  id: i,
+  data: `item-${i}`,
+}));
+const largeQueue = Array.from({ length: 100 }, (_, i) => ({
+  id: i,
+  data: `item-${i}`,
+}));
+
+const queues = [
+  [smallQueue, "small (5)"],
+  [mediumQueue, "medium (20)"],
+  [largeQueue, "large (100)"],
+] as const;
+
+describe.each(queues)("$1", (queue) => {
+  bench("shift() approach", () => {
+    const q = [...queue];
+    while (q.length) q.shift();
+  });
+
+  bench("index approach", () => {
+    const q = [...queue];
+    for (let idx = 0; idx < q.length; idx++) q[idx]; // eslint-disable-line @typescript-eslint/no-unused-expressions
+  });
+
+  bench("pop() reverse", () => {
+    const q = [...queue].reverse();
+    while (q.length) q.pop();
+  });
+
+  bench("forEach", () => {
+    const q = [...queue];
+    q.forEach(() => {});
+  });
+});
diff --git a/express-zod-api/src/deep-checks.ts b/express-zod-api/src/deep-checks.ts
index 0b167ad15..7a4eb2586 100644
--- a/express-zod-api/src/deep-checks.ts
+++ b/express-zod-api/src/deep-checks.ts
@@ -39,8 +39,8 @@ export const hasCycle = (
 ) => {
   const json = z.toJSONSchema(subject, { io, unrepresentable: "any" });
   const stack: unknown[] = [json];
-  while (stack.length) {
-    const entry = stack.shift()!;
+  for (let idx = 0; idx < stack.length; idx++) {
+    const entry = stack[idx];
     if (R.is(Object, entry)) {
       if ((entry as z.core.JSONSchema.BaseSchema).$ref === "#") return true;
       stack.push(...R.values(entry));
diff --git a/express-zod-api/src/diagnostics.ts b/express-zod-api/src/diagnostics.ts
index 6e96515b7..c21b602fe 100644
--- a/express-zod-api/src/diagnostics.ts
+++ b/express-zod-api/src/diagnostics.ts
@@ -29,8 +29,8 @@ export class Diagnostics {
       const stack: z.core.JSONSchema.BaseSchema[] = [
         z.toJSONSchema(endpoint[`${dir}Schema`], { unrepresentable: "any" }),
       ];
-      while (stack.length > 0) {
-        const entry = stack.shift()!;
+      for (let idx = 0; idx < stack.length; idx++) {
+        const entry = stack[idx];
         if (entry.type && entry.type !== "object")
           this.logger.warn(`Endpoint ${dir} schema is not object-based`, ctx);
         for (const prop of ["allOf", "oneOf", "anyOf"] as const)
diff --git a/express-zod-api/src/documentation-helpers.ts b/express-zod-api/src/documentation-helpers.ts
index c9a646929..cf9b78c26 100644
--- a/express-zod-api/src/documentation-helpers.ts
+++ b/express-zod-api/src/documentation-helpers.ts
@@ -371,8 +371,8 @@ const fixReferences = (
   ctx: OpenAPIContext,
 ) => {
   const stack: unknown[] = [subject, defs];
-  while (stack.length) {
-    const entry = stack.shift()!;
+  for (let idx = 0; idx < stack.length; idx++) {
+    const entry = stack[idx];
     if (R.is(Object, entry)) {
       if (isReferenceObject(entry) && !entry.$ref.startsWith("#/components")) {
         const actualName = entry.$ref.split("/").pop()!;
diff --git a/express-zod-api/src/integration.ts b/express-zod-api/src/integration.ts
index 1fe253e34..46f50438c 100644
--- a/express-zod-api/src/integration.ts
+++ b/express-zod-api/src/integration.ts
@@ -153,6 +153,7 @@ export class Integration extends IntegrationBase {
       config,
       onEndpoint: hasHeadMethod ? withHead(onEndpoint) : onEndpoint,
     });
+    // eslint-disable-next-line no-restricted-syntax -- accumulated late, acceptable for generator
     this.#program.unshift(...this.#aliases.values());
     this.#program.push(
       this.makePathType(),
diff --git a/express-zod-api/src/json-schema-helpers.ts b/express-zod-api/src/json-schema-helpers.ts
index daa103505..3eceb01a1 100644
--- a/express-zod-api/src/json-schema-helpers.ts
+++ b/express-zod-api/src/json-schema-helpers.ts
@@ -107,8 +107,8 @@ export const flattenIO = (
   const stack: Stack = [R.pair(false, jsonSchema)]; // [isOptional, JSON Schema]
   const flat: FlattenObjectSchema = { type: "object", properties: {} };
   const flatRequired: string[] = [];
-  while (stack.length) {
-    const [isOptional, entry] = stack.shift()!;
+  for (let idx = 0; idx < stack.length; idx++) {
+    const [isOptional, entry] = stack[idx];
     if (entry.description) flat.description ??= entry.description;
     stack.push(...processAllOf(entry, mode, isOptional));
     stack.push(...processVariants(entry));
diff --git a/express-zod-api/src/routing-walker.ts b/express-zod-api/src/routing-walker.ts
index 9dba9564e..27f1177b8 100644
--- a/express-zod-api/src/routing-walker.ts
+++ b/express-zod-api/src/routing-walker.ts
@@ -91,8 +91,8 @@ export const walkRouting = ({
 }: RoutingWalkerParams) => {
   const stack = processEntries(config, routing);
   const visited = new Set<string>();
-  while (stack.length) {
-    const [path, element, explicitMethod] = stack.shift()!;
+  for (let idx = 0; idx < stack.length; idx++) {
+    const [path, element, explicitMethod] = stack[idx];
     if (element instanceof AbstractEndpoint) {
       if (explicitMethod) {
         checkDuplicate(explicitMethod, path, visited);
@@ -110,7 +110,7 @@ export const walkRouting = ({
       if (element instanceof ServeStatic) {
         if (onStatic) element.apply(path, onStatic);
       } else {
-        stack.unshift(...processEntries(config, element, path));
+        stack.splice(idx + 1, 0, ...processEntries(config, element, path));
       }
     }
   }
diff --git a/express-zod-api/src/routing.ts b/express-zod-api/src/routing.ts
index c9b5d7cea..7011b9ab9 100644
--- a/express-zod-api/src/routing.ts
+++ b/express-zod-api/src/routing.ts
@@ -89,15 +89,9 @@ export const initRouting = ({ app, config, getLogger, ...rest }: InitProps) => {
     /** @link https://github.com/RobinTail/express-zod-api/discussions/2791#discussioncomment-13745912 */
     if (accessMethods.includes("get")) accessMethods.push("head");
     for (const [method, [matchingParsers, endpoint]] of methods) {
-      const handlers = matchingParsers
-        .slice() // must be immutable
-        .concat(async (request, response) => {
-          const logger = getLogger(request);
-          return endpoint.execute({ request, response, logger, config });
-        });
+      const handlers: RequestHandler[] = []; // issue #2706: CORS must go before parsers:
       if (config.cors) {
-        // issue #2706, must go before parsers:
-        handlers.unshift(async (request, response, next) => {
+        handlers.push(async (request, response, next) => {
           const logger = getLogger(request);
           const defaultHeaders = makeCorsHeaders(accessMethods);
           const headers =
@@ -108,6 +102,10 @@ export const initRouting = ({ app, config, getLogger, ...rest }: InitProps) => {
           next();
         });
       }
+      handlers.push(...matchingParsers, async (request, response) => {
+        const logger = getLogger(request);
+        return endpoint.execute({ request, response, logger, config });
+      });
       app[method](path, ...handlers);
     }
     if (config.wrongMethodBehavior === 404) continue;
diff --git a/express-zod-api/src/zts.ts b/express-zod-api/src/zts.ts
index db4d7e36a..0b82f8dc2 100644
--- a/express-zod-api/src/zts.ts
+++ b/express-zod-api/src/zts.ts
@@ -40,27 +40,27 @@ const onTemplateLiteral: Producer = (
   { _zod: { def } }: z.core.$ZodTemplateLiteral,
   { next, api },
 ) => {
-  const parts = [...def.parts];
-  const shiftText = () => {
+  const { parts } = def;
+  let idx = 0;
+  const readText = () => {
     let text = "";
-    while (parts.length) {
-      const part = parts.shift();
-      if (isSchema(part)) {
-        parts.unshift(part);
-        break;
-      }
+    while (idx < parts.length) {
+      const part = parts[idx];
+      if (isSchema(part)) break;
+      idx++;
       text += part ?? ""; // Handle potential undefined values
     }
     return text;
   };
-  const head = api.f.createTemplateHead(shiftText());
+  const head = api.f.createTemplateHead(readText());
   const spans: ts.TemplateLiteralTypeSpan[] = [];
-  while (parts.length) {
-    const schema = next(parts.shift() as z.core.$ZodType);
-    const text = shiftText();
-    const textWrapper = parts.length
-      ? api.f.createTemplateMiddle
-      : api.f.createTemplateTail;
+  while (idx < parts.length) {
+    const schema = next(parts[idx++] as z.core.$ZodType);
+    const text = readText();
+    const textWrapper =
+      idx < parts.length
+        ? api.f.createTemplateMiddle
+        : api.f.createTemplateTail;
     spans.push(api.f.createTemplateLiteralTypeSpan(schema, textWrapper(text)));
   }
   if (!spans.length) return api.makeLiteralType(head.text);
diff --git a/express-zod-api/tests/__snapshots__/routing-walker.spec.ts.snap b/express-zod-api/tests/__snapshots__/routing-walker.spec.ts.snap
new file mode 100644
index 000000000..260b71ae6
--- /dev/null
+++ b/express-zod-api/tests/__snapshots__/routing-walker.spec.ts.snap
@@ -0,0 +1,36 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`walkRouting() > should process endpoints in depth-first order 0 1`] = `
+[
+  [
+    "get",
+    "/v1/user/retrieve",
+    Endpoint {},
+  ],
+  [
+    "get",
+    "/v1/user/create",
+    Endpoint {},
+  ],
+  [
+    "get",
+    "/v1/record",
+    Endpoint {},
+  ],
+]
+`;
+
+exports[`walkRouting() > should process endpoints in depth-first order 1 1`] = `
+[
+  [
+    "get",
+    "/a/b/c",
+    Endpoint {},
+  ],
+  [
+    "get",
+    "/a/d",
+    Endpoint {},
+  ],
+]
+`;
diff --git a/express-zod-api/tests/routing-walker.spec.ts b/express-zod-api/tests/routing-walker.spec.ts
new file mode 100644
index 000000000..c10479ddc
--- /dev/null
+++ b/express-zod-api/tests/routing-walker.spec.ts
@@ -0,0 +1,27 @@
+import { defaultEndpointsFactory, Routing } from "../src";
+import { walkRouting } from "../src/routing-walker";
+
+describe("walkRouting()", () => {
+  const endpoint = defaultEndpointsFactory.buildVoid({
+    handler: vi.fn(),
+  });
+
+  const onEndpoint = vi.fn();
+
+  afterEach(() => {
+    onEndpoint.mockClear();
+  });
+
+  test.each<Routing>([
+    {
+      v1: {
+        user: { retrieve: endpoint, create: endpoint },
+        record: endpoint,
+      },
+    },
+    { a: { b: { c: endpoint }, d: endpoint } },
+  ])("should process endpoints in depth-first order %#", (routing) => {
+    walkRouting({ routing, config: { cors: false }, onEndpoint });
+    expect(onEndpoint.mock.calls).toMatchSnapshot();
+  });
+});