diff --git a/apps/web/app/api/availability/calendar/route.ts b/apps/web/app/api/availability/calendar/route.ts
new file mode 100644
index 0000000000..91e37181a4
--- /dev/null
+++ b/apps/web/app/api/availability/calendar/route.ts
@@ -0,0 +1,123 @@
+import { cookies, headers } from "next/headers";
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import { z } from "zod";
+
+import { getCalendarCredentials, getConnectedCalendars } from "@calcom/core/CalendarManager";
+import { getServerSession } from "@calcom/features/auth/lib/getServerSession";
+import { CalendarCache } from "@calcom/features/calendar-cache/calendar-cache";
+import { HttpError } from "@calcom/lib/http-error";
+import notEmpty from "@calcom/lib/notEmpty";
+import { SelectedCalendarRepository } from "@calcom/lib/server/repository/selectedCalendar";
+import { UserRepository } from "@calcom/lib/server/repository/user";
+
+import { buildLegacyRequest } from "@lib/buildLegacyCtx";
+
+const selectedCalendarSelectSchema = z.object({
+  integration: z.string(),
+  externalId: z.string(),
+  credentialId: z.coerce.number(),
+  eventTypeId: z.coerce.number().nullish(),
+});
+
+async function authMiddleware() {
+  const session = await getServerSession({ req: buildLegacyRequest(headers(), cookies()) });
+
+  if (!session?.user?.id) {
+    throw new HttpError({ statusCode: 401, message: "Not authenticated" });
+  }
+
+  const userWithCredentials = await UserRepository.findUserWithCredentials({ id: session.user.id });
+
+  if (!userWithCredentials) {
+    throw new HttpError({ statusCode: 401, message: "Not authenticated" });
+  }
+
+  return userWithCredentials;
+}
+
+// TODO: It doesn't seem to be used from within the app. It is possible that someone outside Cal.com is using this GET endpoint
+export async function GET() {
+  try {
+    const user = await authMiddleware();
+
+    const selectedCalendarIds = await SelectedCalendarRepository.findMany({
+      where: { userId: user.id },
+      select: { externalId: true },
+    });
+    // get user's credentials + their connected integrations
+    const calendarCredentials = getCalendarCredentials(user.credentials);
+    // get all the connected integrations' calendars (from third party)
+    const { connectedCalendars } = await getConnectedCalendars(
+      calendarCredentials,
+      user.userLevelSelectedCalendars
+    );
+
+    const calendars = connectedCalendars.flatMap((c) => c.calendars).filter(notEmpty);
+    const selectableCalendars = calendars.map((cal) => {
+      return { selected: selectedCalendarIds.findIndex((s) => s.externalId === cal.externalId) > -1, ...cal };
+    });
+
+    return NextResponse.json(selectableCalendars);
+  } catch (error) {
+    if (error instanceof HttpError) {
+      throw error;
+    }
+    return NextResponse.json({ error: "Internal Server Error" }, { status: 500 });
+  }
+}
+
+export async function POST(req: NextRequest) {
+  try {
+    const user = await authMiddleware();
+    const body = await req.json();
+    const { integration, externalId, credentialId, eventTypeId } = selectedCalendarSelectSchema.parse(body);
+
+    await SelectedCalendarRepository.upsert({
+      userId: user.id,
+      integration,
+      externalId,
+      credentialId,
+      eventTypeId: eventTypeId ?? null,
+    });
+
+    return NextResponse.json({ message: "Calendar Selection Saved" });
+  } catch (error) {
+    if (error instanceof HttpError) {
+      throw error;
+    }
+    return NextResponse.json({ error: "Internal Server Error" }, { status: 500 });
+  }
+}
+
+export async function DELETE(req: NextRequest) {
+  try {
+    const user = await authMiddleware();
+    const searchParams = Object.fromEntries(req.nextUrl.searchParams.entries());
+
+    const { integration, externalId, credentialId, eventTypeId } =
+      selectedCalendarSelectSchema.parse(searchParams);
+
+    const calendarCacheRepository = await CalendarCache.initFromCredentialId(credentialId);
+    await calendarCacheRepository.unwatchCalendar({
+      calendarId: externalId,
+      eventTypeIds: [eventTypeId ?? null],
+    });
+
+    await SelectedCalendarRepository.delete({
+      where: {
+        userId: user.id,
+        externalId,
+        integration,
+        eventTypeId: eventTypeId ?? null,
+      },
+    });
+
+    return NextResponse.json({ message: "Calendar Selection Saved" });
+  } catch (error) {
+    if (error instanceof HttpError) {
+      throw error;
+    }
+    return NextResponse.json({ error: "Internal Server Error" }, { status: 500 });
+  }
+}
diff --git a/apps/web/pages/api/availability/calendar.ts b/apps/web/pages/api/availability/calendar.ts
deleted file mode 100644
index 3d975dfc48..0000000000
--- a/apps/web/pages/api/availability/calendar.ts
+++ /dev/null
@@ -1,108 +0,0 @@
-import type { NextApiRequest, NextApiResponse } from "next";
-import { z } from "zod";
-
-import { getCalendarCredentials, getConnectedCalendars } from "@calcom/core/CalendarManager";
-import { getServerSession } from "@calcom/features/auth/lib/getServerSession";
-import { CalendarCache } from "@calcom/features/calendar-cache/calendar-cache";
-import { HttpError } from "@calcom/lib/http-error";
-import notEmpty from "@calcom/lib/notEmpty";
-import { defaultHandler, defaultResponder } from "@calcom/lib/server";
-import { SelectedCalendarRepository } from "@calcom/lib/server/repository/selectedCalendar";
-import { UserRepository } from "@calcom/lib/server/repository/user";
-
-const selectedCalendarSelectSchema = z.object({
-  integration: z.string(),
-  externalId: z.string(),
-  credentialId: z.coerce.number(),
-  eventTypeId: z.coerce.number().nullish(),
-});
-
-/** Shared authentication middleware for GET, DELETE and POST requests */
-async function authMiddleware(req: CustomNextApiRequest) {
-  const session = await getServerSession({ req });
-
-  if (!session?.user?.id) {
-    throw new HttpError({ statusCode: 401, message: "Not authenticated" });
-  }
-
-  const userWithCredentials = await UserRepository.findUserWithCredentials({ id: session.user.id });
-
-  if (!userWithCredentials) {
-    throw new HttpError({ statusCode: 401, message: "Not authenticated" });
-  }
-  req.userWithCredentials = userWithCredentials;
-  return userWithCredentials;
-}
-
-type CustomNextApiRequest = NextApiRequest & {
-  userWithCredentials?: Awaited<ReturnType<typeof authMiddleware>>;
-};
-
-async function postHandler(req: CustomNextApiRequest) {
-  if (!req.userWithCredentials) throw new HttpError({ statusCode: 401, message: "Not authenticated" });
-  const user = req.userWithCredentials;
-  const { integration, externalId, credentialId, eventTypeId } = selectedCalendarSelectSchema.parse(req.body);
-  await SelectedCalendarRepository.upsert({
-    userId: user.id,
-    integration,
-    externalId,
-    credentialId,
-    eventTypeId: eventTypeId ?? null,
-  });
-
-  return { message: "Calendar Selection Saved" };
-}
-
-async function deleteHandler(req: CustomNextApiRequest) {
-  if (!req.userWithCredentials) throw new HttpError({ statusCode: 401, message: "Not authenticated" });
-  const user = req.userWithCredentials;
-  const { integration, externalId, credentialId, eventTypeId } = selectedCalendarSelectSchema.parse(
-    req.query
-  );
-  const calendarCacheRepository = await CalendarCache.initFromCredentialId(credentialId);
-  await calendarCacheRepository.unwatchCalendar({
-    calendarId: externalId,
-    eventTypeIds: [eventTypeId ?? null],
-  });
-  await SelectedCalendarRepository.delete({
-    where: {
-      userId: user.id,
-      externalId,
-      integration,
-      eventTypeId: eventTypeId ?? null,
-    },
-  });
-
-  return { message: "Calendar Selection Saved" };
-}
-
-// TODO: It doesn't seem to be used from within the app. It is possible that someone outside Cal.com is using this GET endpoint
-async function getHandler(req: CustomNextApiRequest) {
-  if (!req.userWithCredentials) throw new HttpError({ statusCode: 401, message: "Not authenticated" });
-  const user = req.userWithCredentials;
-  const selectedCalendarIds = await SelectedCalendarRepository.findMany({
-    where: { userId: user.id },
-    select: { externalId: true },
-  });
-  // get user's credentials + their connected integrations
-  const calendarCredentials = getCalendarCredentials(user.credentials);
-  // get all the connected integrations' calendars (from third party)
-  const { connectedCalendars } = await getConnectedCalendars(
-    calendarCredentials,
-    user.userLevelSelectedCalendars
-  );
-  const calendars = connectedCalendars.flatMap((c) => c.calendars).filter(notEmpty);
-  const selectableCalendars = calendars.map((cal) => {
-    return { selected: selectedCalendarIds.findIndex((s) => s.externalId === cal.externalId) > -1, ...cal };
-  });
-  return selectableCalendars;
-}
-
-export default defaultResponder(async (req: NextApiRequest, res: NextApiResponse) => {
-  await authMiddleware(req);
-  return defaultHandler({
-    GET: Promise.resolve({ default: defaultResponder(getHandler) }),
-    POST: Promise.resolve({ default: defaultResponder(postHandler) }),
-    DELETE: Promise.resolve({ default: defaultResponder(deleteHandler) }),
-  })(req, res);
-});