diff --git a/api/.eslintrc.js b/api/.eslintrc.js
index 88075e2..53392fa 100644
--- a/api/.eslintrc.js
+++ b/api/.eslintrc.js
@@ -2,6 +2,7 @@ module.exports = {
     extends: ['standard-with-typescript'],
     rules: {
         '@typescript-eslint/indent': ['error', 4],
-        '@typescript-eslint/semi': ['error', 'always']
+        '@typescript-eslint/semi': ['error', 'always'],
+        '@typescript-eslint/strict-boolean-expressions': 'off'
     }
 };
diff --git a/api/src/database.ts b/api/src/database.ts
index 3f64d6c..c209295 100644
--- a/api/src/database.ts
+++ b/api/src/database.ts
@@ -10,6 +10,6 @@ const sequelize = new Sequelize({
 });
 
 sequelize.addModels([Container, Page]);
-sequelize.sync();
+void sequelize.sync();
 
 export default sequelize;
diff --git a/api/src/index.ts b/api/src/index.ts
index 45acba6..372d36a 100644
--- a/api/src/index.ts
+++ b/api/src/index.ts
@@ -16,6 +16,7 @@ import v1Router from './v1';
 
 import './database';
 import { getSitemap } from './utils/sitemap';
+import { wrapAsync } from './utils/express';
 import { Page } from './models';
 
 const app = express();
@@ -24,11 +25,11 @@ const app = express();
 app.use(cors({
     credentials: true,
     origin: [
-        new RegExp('gruppe-adler.de$', 'i'),
-        new RegExp('localhost:[0-9]+$', 'i'),
-        new RegExp('127.0.0.1:[0-9]+$', 'i'),
-        new RegExp('127.0.0.1$', 'i'),
-        new RegExp('localhost$', 'i')
+        /gruppe-adler.de$/i,
+        /localhost:[0-9]+$/i,
+        /127.0.0.1:[0-9]+$/i,
+        /127.0.0.1$/i,
+        /localhost$/i
     ]
 }));
 
@@ -48,7 +49,7 @@ app.use('/api/v1', v1Router);
 
 app.use('/uploads', express.static(join(__dirname, '../data/uploads')));
 
-app.get('/sitemap.xml', async (req, res) => {
+app.get('/sitemap.xml', wrapAsync(async (req, res) => {
     res.header('Content-Type', 'application/xml');
     res.header('Content-Encoding', 'gzip');
 
@@ -59,7 +60,7 @@ app.get('/sitemap.xml', async (req, res) => {
         console.error(err);
         res.status(500).end();
     }
-});
+}));
 
 // frontend
 if (existsSync(join(__dirname, '../frontend'))) {
@@ -86,7 +87,7 @@ if (existsSync(join(__dirname, '../frontend'))) {
         express.static(join(__dirname, '../frontend'), {
             setHeaders: (res: Response, path: string) => {
                 if (/.+\.(?!html).*$/i.test(path)) {
-                    const cacheControl = cacheHeaders[path] || 'public, max-age=2678400';
+                    const cacheControl = cacheHeaders[path] ?? 'public, max-age=2678400';
 
                     res.header('Cache-Control', cacheControl);
                 } else {
@@ -97,7 +98,7 @@ if (existsSync(join(__dirname, '../frontend'))) {
     );
 
     let pages: string[] = [];
-    const cachePages = async () => {
+    const cachePages = async (): Promise<void> => {
         const newPages = await Page.findAll({ attributes: ['slug'] }) as Array<Pick<Page, 'slug'>>;
 
         const slugs = newPages.map(p => p.slug);
@@ -108,7 +109,7 @@ if (existsSync(join(__dirname, '../frontend'))) {
 
     Page.addHook('afterCreate', cachePages);
     Page.addHook('afterDestroy', cachePages);
-    cachePages();
+    void cachePages();
     app.get('*', (req: Request, res: Response, next: NextFunction) => {
         if (!req.accepts('application/html')) {
             next();
diff --git a/api/src/utils/EventsService.ts b/api/src/utils/EventsService.ts
index f246c30..9651373 100644
--- a/api/src/utils/EventsService.ts
+++ b/api/src/utils/EventsService.ts
@@ -21,7 +21,7 @@ export class ArmaEventsService {
     // this constructor is actually important to make sure it is private (singleton pattern)
     // eslint-disable-next-line no-useless-constructor, @typescript-eslint/no-empty-function
     private constructor () {
-        this.cacheEvents();
+        void this.cacheEvents();
 
         // fetch new events every half an hour
         setInterval(this.cacheEvents.bind(this), 1000 * 60 * 30);
diff --git a/api/src/utils/express.ts b/api/src/utils/express.ts
index 72b2c1a..fe51b2f 100644
--- a/api/src/utils/express.ts
+++ b/api/src/utils/express.ts
@@ -2,7 +2,9 @@ import { type Request, type Response, type NextFunction, type RequestHandler } f
 import { validationResult } from 'express-validator';
 import ResponseError from './ResponseError';
 
-export const wrapAsync = (fn: RequestHandler): RequestHandler => (req: Request, res: Response, next: NextFunction): void => {
+type AsyncRequestHandler = (...params: Parameters<RequestHandler>) => Promise<ReturnType<RequestHandler>>;
+
+export const wrapAsync = (fn: AsyncRequestHandler): RequestHandler => (req: Request, res: Response, next: NextFunction): void => {
     // Make sure to `.catch()` any errors and pass them along to the `next()`
     // middleware in the chain, in this case the error handler.
     fn(req, res, next).catch(next);
diff --git a/api/src/utils/sso.ts b/api/src/utils/sso.ts
index 8d4d279..fc8fd14 100644
--- a/api/src/utils/sso.ts
+++ b/api/src/utils/sso.ts
@@ -42,7 +42,7 @@ async function fetchUser (token: string): Promise<SSOUser | null> {
     return json.data.authenticate;
 }
 
-async function validateToken (token: string) {
+async function validateToken (token: string): Promise<void> {
     const user = await fetchUser(token);
 
     if (user === null) throw new ReponseError(401);