diff --git a/packages/google-cloud-serverless/src/gcpfunction/events.ts b/packages/google-cloud-serverless/src/gcpfunction/events.ts
index 319329ccf28f..1ac9115b0817 100644
--- a/packages/google-cloud-serverless/src/gcpfunction/events.ts
+++ b/packages/google-cloud-serverless/src/gcpfunction/events.ts
@@ -22,16 +22,15 @@ export function wrapEventFunction(
   return proxyFunction(fn, f => domainify(_wrapEventFunction(f, wrapOptions)));
 }
 
-/** */
 function _wrapEventFunction<F extends EventFunction | EventFunctionWithCallback>(
   fn: F,
   wrapOptions: Partial<EventFunctionWrapperOptions> = {},
-): (...args: Parameters<F>) => ReturnType<F> | Promise<void> {
+): (...args: Parameters<F>) => void | Promise<void> {
   const options: EventFunctionWrapperOptions = {
     flushTimeout: 2000,
     ...wrapOptions,
   };
-  return (...eventFunctionArguments: Parameters<F>): ReturnType<F> | Promise<void> => {
+  return (...eventFunctionArguments: Parameters<F>): void | Promise<void> => {
     const [data, context, callback] = eventFunctionArguments;
 
     return startSpanManual(
@@ -47,8 +46,8 @@ function _wrapEventFunction<F extends EventFunction | EventFunctionWithCallback>
         const scope = getCurrentScope();
         scope.setContext('gcp.function.context', { ...context });
 
-        const newCallback = domainify((...args: unknown[]) => {
-          if (args[0] !== null && args[0] !== undefined) {
+        const newCallback = domainify((...args): void => {
+          if (args[0] != null) {
             captureException(args[0], scope => markEventUnhandled(scope));
           }
           span.end();
diff --git a/packages/google-cloud-serverless/src/gcpfunction/general.ts b/packages/google-cloud-serverless/src/gcpfunction/general.ts
index f819bd5aaaf3..2c9a7df3e698 100644
--- a/packages/google-cloud-serverless/src/gcpfunction/general.ts
+++ b/packages/google-cloud-serverless/src/gcpfunction/general.ts
@@ -1,24 +1,20 @@
 import type { Request, Response } from 'express';
 
-export interface HttpFunction {
-  (req: Request, res: Response): any; // eslint-disable-line @typescript-eslint/no-explicit-any
-}
+export type HttpFunction = (req: Request, res: Response) => void;
 
-export interface EventFunction {
-  (data: Record<string, any>, context: Context): any; // eslint-disable-line @typescript-eslint/no-explicit-any
-}
+export type EventFunction = (data: Record<string, unknown>, context: Context) => void;
 
-export interface EventFunctionWithCallback {
-  (data: Record<string, any>, context: Context, callback: Function): any; // eslint-disable-line @typescript-eslint/no-explicit-any, @typescript-eslint/ban-types
-}
+export type EventFunctionWithCallback = (
+  data: Record<string, unknown>,
+  context: Context,
+  // eslint-disable-next-line @typescript-eslint/ban-types
+  callback: Function,
+) => void;
 
-export interface CloudEventFunction {
-  (cloudevent: CloudEventsContext): any; // eslint-disable-line @typescript-eslint/no-explicit-any
-}
+export type CloudEventFunction = (cloudevent: CloudEventsContext) => void;
 
-export interface CloudEventFunctionWithCallback {
-  (cloudevent: CloudEventsContext, callback: Function): any; // eslint-disable-line @typescript-eslint/no-explicit-any, @typescript-eslint/ban-types
-}
+// eslint-disable-next-line @typescript-eslint/ban-types
+export type CloudEventFunctionWithCallback = (cloudevent: CloudEventsContext, callback: Function) => void;
 
 export interface CloudFunctionsContext {
   eventId?: string;
diff --git a/packages/google-cloud-serverless/src/utils.ts b/packages/google-cloud-serverless/src/utils.ts
index 8e33f55b51cd..f55569c82f9b 100644
--- a/packages/google-cloud-serverless/src/utils.ts
+++ b/packages/google-cloud-serverless/src/utils.ts
@@ -17,14 +17,14 @@ export function domainify<A extends unknown[], R>(fn: (...args: A) => R): (...ar
  * @returns wrapped function
  */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
-export function proxyFunction<A extends any[], R, F extends (...args: A) => R>(
+export function proxyFunction<F extends (...args: any[]) => unknown>(
   source: F,
   wrap: (source: F) => F,
   overrides?: Record<PropertyKey, unknown>,
 ): F {
   const wrapper = wrap(source);
   const handler: ProxyHandler<F> = {
-    apply: <T>(_target: F, thisArg: T, args: A) => {
+    apply: <T>(_target: F, thisArg: T, args: Parameters<F>) => {
       return wrapper.apply(thisArg, args);
     },
   };