diff --git a/src/clients/geocoding/osm.ts b/src/clients/geocoding/osm.ts
index 12e28cd..deceb47 100644
--- a/src/clients/geocoding/osm.ts
+++ b/src/clients/geocoding/osm.ts
@@ -3,8 +3,9 @@ import NodeGeocoder from 'node-geocoder';
 import fetch from 'node-fetch';
 import PQueue from 'p-queue';
 import { mean } from '../../utils/math';
+import type { Geocoder } from './types';
 
-export const createOsmClient = () => {
+export const createOsmClient = (): Geocoder => {
     const geocoder = NodeGeocoder({
         provider: 'openstreetmap',
         fetch: (url, options) => {
@@ -28,7 +29,7 @@ export const createOsmClient = () => {
     });
 
     return {
-        geocode: async (query: string) => {
+        geocode: async (query) => {
             const result = await queue.add(() => geocoder.geocode(query));
 
             if (!result.length) {
diff --git a/src/clients/geocoding/types.ts b/src/clients/geocoding/types.ts
new file mode 100644
index 0000000..ffc8086
--- /dev/null
+++ b/src/clients/geocoding/types.ts
@@ -0,0 +1,6 @@
+export type Geocoder = {
+    geocode(query: string): Promise<{
+        longitude: number;
+        latitude: number;
+    }>;
+};
diff --git a/src/storage/cache.ts b/src/storage/cache.ts
index 04eeacb..03c2228 100644
--- a/src/storage/cache.ts
+++ b/src/storage/cache.ts
@@ -1,6 +1,6 @@
 import { throttle } from '../utils/throttle';
-import { StringifiableValue, createSerializer } from '../utils/serializer';
-import { ClearableKeyValueStorage } from './types';
+import { type StringifiableValue, createSerializer } from '../utils/serializer';
+import type { ClearableKeyValueStorage } from './types';
 
 type DataProvider<TKey, TValue> = (key: TKey) => Promise<TValue>;
 
@@ -20,7 +20,7 @@ export const createCachedDataProvider = <
     cacheStorage: ClearableKeyValueStorage<string, CacheEntry<TValue>>;
     getNewValue: DataProvider<TKey, TValue>;
     ttlMs: number;
-}) => {
+}): DataProvider<TKey, TValue> => {
     const keySerializer = createSerializer<TKey>();
     const unsafeGet = async (key: TKey) => {
         const cacheEntry = await cacheStorage.get(keySerializer.stringify(key));
diff --git a/src/storage/inMemoryDB.ts b/src/storage/inMemoryDB.ts
index 432d3a6..ebc1626 100644
--- a/src/storage/inMemoryDB.ts
+++ b/src/storage/inMemoryDB.ts
@@ -1,10 +1,10 @@
 import { sleep } from '../utils/eventLoop';
-import { StringifiableValue, createSerializer } from '../utils/serializer';
-import { ClearableKeyValueStorage } from './types';
+import { type StringifiableValue, createSerializer } from '../utils/serializer';
+import type { ClearableKeyValueStorage } from './types';
 
 export const createKeyValueStorage = <TValue extends StringifiableValue>(
     latencyMs: number,
-) => {
+): ClearableKeyValueStorage<string, TValue> => {
     const withSimulatedLatency = async <TResult>(
         f: () => Promise<TResult>,
     ): Promise<TResult> => {
@@ -17,7 +17,7 @@ export const createKeyValueStorage = <TValue extends StringifiableValue>(
     const serializer = createSerializer<TValue>();
     const storage = new Map<string, string>();
     return {
-        get: (key: string) =>
+        get: (key) =>
             withSimulatedLatency(() =>
                 Promise.resolve(
                     storage.has(key)
@@ -32,7 +32,7 @@ export const createKeyValueStorage = <TValue extends StringifiableValue>(
                           },
                 ),
             ),
-        set: (key: string, value: TValue) =>
+        set: (key, value) =>
             withSimulatedLatency(() =>
                 Promise.resolve(
                     void storage.set(key, serializer.stringify(value)),
@@ -41,5 +41,5 @@ export const createKeyValueStorage = <TValue extends StringifiableValue>(
         clear: () =>
             // eslint-disable-next-line @typescript-eslint/no-confusing-void-expression
             withSimulatedLatency(() => Promise.resolve(storage.clear())),
-    } as ClearableKeyValueStorage<string, TValue>;
+    };
 };
diff --git a/src/utils/throttle.ts b/src/utils/throttle.ts
index 4db2f03..8e10bd6 100644
--- a/src/utils/throttle.ts
+++ b/src/utils/throttle.ts
@@ -23,10 +23,10 @@ import { StringifiableValue, createSerializer } from './serializer';
  */
 export const throttle = <TArgs extends StringifiableValue[], TResult>(
     f: (...args: TArgs) => Promise<TResult>,
-) => {
+): ((...args: TArgs) => Promise<TResult>) => {
     const argsSerializer = createSerializer<TArgs>();
     const promises = new Map<string, Promise<TResult>>();
-    return (...args: TArgs) => {
+    return (...args) => {
         const promiseKey = argsSerializer.stringify(args);
         if (!promises.has(promiseKey)) {
             promises.set(