diff --git a/src/controllers/api/getFriendsController.ts b/src/controllers/api/getFriendsController.ts
index c0ec7b33..292e107c 100644
--- a/src/controllers/api/getFriendsController.ts
+++ b/src/controllers/api/getFriendsController.ts
@@ -1,6 +1,6 @@
 import { Request, Response } from "express";
 
-const getFriendsController = (_request: Request, response: Response) => {
+const getFriendsController = (_request: Request, response: Response): void => {
     response.writeHead(200, {
         //Connection: "keep-alive",
         //"Content-Encoding": "gzip",
diff --git a/src/helpers/inventoryHelpers.ts b/src/helpers/inventoryHelpers.ts
index 4a48474f..d85fc978 100644
--- a/src/helpers/inventoryHelpers.ts
+++ b/src/helpers/inventoryHelpers.ts
@@ -1,4 +1,4 @@
-import { IOid } from "@/src/types/commonTypes";
+import { IMongoDate, IOid } from "@/src/types/commonTypes";
 import { IInventoryResponse } from "@/src/types/inventoryTypes/inventoryTypes";
 import { Types } from "mongoose";
 
@@ -13,6 +13,6 @@ export const toOid = (objectId: Types.ObjectId): IOid => {
     return { $oid: objectId.toString() } satisfies IOid;
 };
 
-export const toMongoDate = (date: Date) => {
+export const toMongoDate = (date: Date): IMongoDate => {
     return { $date: { $numberLong: date.getTime().toString() } };
 };
diff --git a/src/helpers/purchaseHelpers.ts b/src/helpers/purchaseHelpers.ts
index 161bb2ec..3fbcaf52 100644
--- a/src/helpers/purchaseHelpers.ts
+++ b/src/helpers/purchaseHelpers.ts
@@ -5,7 +5,7 @@ export const isSlotPurchaseName = (slotPurchaseName: string): slotPurchaseName i
     return slotPurchaseName in slotPurchaseNameToSlotName;
 };
 
-export const parseSlotPurchaseName = (slotPurchaseName: string) => {
+export const parseSlotPurchaseName = (slotPurchaseName: string): SlotPurchaseName => {
     if (!isSlotPurchaseName(slotPurchaseName)) throw new Error(`invalid slot name ${slotPurchaseName}`);
     return slotPurchaseName;
 };
diff --git a/src/helpers/stringHelpers.ts b/src/helpers/stringHelpers.ts
index ea6e47ef..89a3ae9d 100644
--- a/src/helpers/stringHelpers.ts
+++ b/src/helpers/stringHelpers.ts
@@ -17,7 +17,7 @@ export const getSubstringFromKeywordToKeyword = (str: string, keywordBegin: stri
     return str.substring(beginIndex, endIndex + 1);
 };
 
-export const getIndexAfter = (str: string, searchWord: string) => {
+export const getIndexAfter = (str: string, searchWord: string): number => {
     const index = str.indexOf(searchWord);
     if (index === -1) {
         return -1;
diff --git a/src/middleware/middleware.ts b/src/middleware/middleware.ts
index 68e60191..96fe391c 100644
--- a/src/middleware/middleware.ts
+++ b/src/middleware/middleware.ts
@@ -1,7 +1,7 @@
 import { logger } from "@/src/utils/logger";
 import { /*NextFunction,*/ Request, Response } from "express";
 
-const unknownEndpointHandler = (request: Request, response: Response) => {
+const unknownEndpointHandler = (request: Request, response: Response): void => {
     logger.error(`unknown endpoint ${request.method} ${request.path}`);
     if (request.body) {
         logger.debug(`data provided to ${request.path}: ${String(request.body)}`);
diff --git a/src/models/inventoryModels/inventoryModel.ts b/src/models/inventoryModels/inventoryModel.ts
index d67e474a..5e5a1680 100644
--- a/src/models/inventoryModels/inventoryModel.ts
+++ b/src/models/inventoryModels/inventoryModel.ts
@@ -326,7 +326,7 @@ const MailboxSchema = new Schema<IMailbox>(
     {
         LastInboxId: {
             type: Schema.Types.ObjectId,
-            set: (v: IMailbox["LastInboxId"]) => v.$oid.toString()
+            set: (v: IMailbox["LastInboxId"]): string => v.$oid.toString()
         }
     },
     { id: false, _id: false }
diff --git a/src/services/configService.ts b/src/services/configService.ts
index 2cd7b3c5..29d513d2 100644
--- a/src/services/configService.ts
+++ b/src/services/configService.ts
@@ -56,7 +56,7 @@ interface ILoggerConfig {
     level: string; // "fatal" | "error" | "warn" | "info" | "http" | "debug" | "trace";
 }
 
-export const updateConfig = async (data: string) => {
+export const updateConfig = async (data: string): Promise<void> => {
     amnesia = true;
     await fsPromises.writeFile(configPath, data);
     Object.assign(config, JSON.parse(data));
diff --git a/src/services/inventoryService.ts b/src/services/inventoryService.ts
index d41e7ee7..381da0c5 100644
--- a/src/services/inventoryService.ts
+++ b/src/services/inventoryService.ts
@@ -47,7 +47,7 @@ import { handleStoreItemAcquisition } from "./purchaseService";
 export const createInventory = async (
     accountOwnerId: Types.ObjectId,
     defaultItemReferences: { loadOutPresetId: Types.ObjectId; ship: Types.ObjectId }
-) => {
+): Promise<void> => {
     try {
         const inventory = config.skipTutorial
             ? new Inventory({
@@ -367,7 +367,7 @@ export const addItem = async (
 };
 
 //TODO: maybe genericMethod for all the add methods, they share a lot of logic
-export const addSentinel = async (sentinelName: string, accountId: string) => {
+export const addSentinel = async (sentinelName: string, accountId: string): Promise<IInventoryChanges> => {
     const inventoryChanges: IInventoryChanges = {};
 
     if (ExportSentinels[sentinelName]?.defaultWeapon) {
@@ -400,11 +400,11 @@ export const addSentinel = async (sentinelName: string, accountId: string) => {
     return inventoryChanges;
 };
 
-export const addSentinelWeapon = async (typeName: string, accountId: string) => {
+export const addSentinelWeapon = async (typeName: string, accountId: string): Promise<IEquipmentClient> => {
     const inventory = await getInventory(accountId);
     const sentinelIndex = inventory.SentinelWeapons.push({ ItemType: typeName });
     const changedInventory = await inventory.save();
-    return changedInventory.SentinelWeapons[sentinelIndex - 1].toJSON();
+    return changedInventory.SentinelWeapons[sentinelIndex - 1].toJSON<IEquipmentClient>();
 };
 
 export const addPowerSuit = async (powersuitName: string, accountId: string): Promise<IInventoryChanges> => {
@@ -458,14 +458,19 @@ export const addSpecialItem = async (
     (inventoryChanges.SpecialItems as object[]).push(changedInventory.SpecialItems[specialItemIndex - 1].toJSON());
 };
 
-export const addSpaceSuit = async (spacesuitName: string, accountId: string) => {
+export const addSpaceSuit = async (spacesuitName: string, accountId: string): Promise<IEquipmentClient> => {
     const inventory = await getInventory(accountId);
     const suitIndex = inventory.SpaceSuits.push({ ItemType: spacesuitName, Configs: [], UpgradeVer: 101, XP: 0 });
     const changedInventory = await inventory.save();
-    return changedInventory.SpaceSuits[suitIndex - 1].toJSON();
+    return changedInventory.SpaceSuits[suitIndex - 1].toJSON<IEquipmentClient>();
 };
 
-export const updateSlots = async (accountId: string, slotName: SlotNames, slotAmount: number, extraAmount: number) => {
+export const updateSlots = async (
+    accountId: string,
+    slotName: SlotNames,
+    slotAmount: number,
+    extraAmount: number
+): Promise<void> => {
     const inventory = await getInventory(accountId);
 
     inventory[slotName].Slots += slotAmount;
@@ -542,7 +547,7 @@ export const updateGeneric = async (data: IGenericUpdate, accountId: string): Pr
     await inventory.save();
 };
 
-export const updateTheme = async (data: IThemeUpdateRequest, accountId: string) => {
+export const updateTheme = async (data: IThemeUpdateRequest, accountId: string): Promise<void> => {
     const inventory = await getInventory(accountId);
     if (data.Style) inventory.ThemeStyle = data.Style;
     if (data.Background) inventory.ThemeBackground = data.Background;
@@ -634,7 +639,7 @@ const addGearExpByCategory = (
     inventory: IInventoryDatabaseDocument,
     gearArray: IEquipmentClient[] | undefined,
     categoryName: TEquipmentKey
-) => {
+): void => {
     const category = inventory[categoryName];
 
     gearArray?.forEach(({ ItemId, XP }) => {
@@ -663,7 +668,7 @@ const addGearExpByCategory = (
     });
 };
 
-export const addMiscItems = (inventory: IInventoryDatabaseDocument, itemsArray: IMiscItem[] | undefined) => {
+export const addMiscItems = (inventory: IInventoryDatabaseDocument, itemsArray: IMiscItem[] | undefined): void => {
     const { MiscItems } = inventory;
 
     itemsArray?.forEach(({ ItemCount, ItemType }) => {
@@ -678,7 +683,10 @@ export const addMiscItems = (inventory: IInventoryDatabaseDocument, itemsArray:
     });
 };
 
-export const addShipDecorations = (inventory: IInventoryDatabaseDocument, itemsArray: IConsumable[] | undefined) => {
+export const addShipDecorations = (
+    inventory: IInventoryDatabaseDocument,
+    itemsArray: IConsumable[] | undefined
+): void => {
     const { ShipDecorations } = inventory;
 
     itemsArray?.forEach(({ ItemCount, ItemType }) => {
@@ -693,7 +701,7 @@ export const addShipDecorations = (inventory: IInventoryDatabaseDocument, itemsA
     });
 };
 
-export const addConsumables = (inventory: IInventoryDatabaseDocument, itemsArray: IConsumable[] | undefined) => {
+export const addConsumables = (inventory: IInventoryDatabaseDocument, itemsArray: IConsumable[] | undefined): void => {
     const { Consumables } = inventory;
 
     itemsArray?.forEach(({ ItemCount, ItemType }) => {
@@ -708,7 +716,7 @@ export const addConsumables = (inventory: IInventoryDatabaseDocument, itemsArray
     });
 };
 
-export const addRecipes = (inventory: IInventoryDatabaseDocument, itemsArray: ITypeCount[] | undefined) => {
+export const addRecipes = (inventory: IInventoryDatabaseDocument, itemsArray: ITypeCount[] | undefined): void => {
     const { Recipes } = inventory;
 
     itemsArray?.forEach(({ ItemCount, ItemType }) => {
@@ -723,7 +731,7 @@ export const addRecipes = (inventory: IInventoryDatabaseDocument, itemsArray: IT
     });
 };
 
-export const addMods = (inventory: IInventoryDatabaseDocument, itemsArray: IRawUpgrade[] | undefined) => {
+export const addMods = (inventory: IInventoryDatabaseDocument, itemsArray: IRawUpgrade[] | undefined): void => {
     const { RawUpgrades } = inventory;
     itemsArray?.forEach(({ ItemType, ItemCount }) => {
         const itemIndex = RawUpgrades.findIndex(i => i.ItemType === ItemType);
@@ -740,7 +748,7 @@ export const addMods = (inventory: IInventoryDatabaseDocument, itemsArray: IRawU
 export const addFusionTreasures = (
     inventory: IInventoryDatabaseDocument,
     itemsArray: IFusionTreasure[] | undefined
-) => {
+): void => {
     const { FusionTreasures } = inventory;
     itemsArray?.forEach(({ ItemType, ItemCount, Sockets }) => {
         const itemIndex = FusionTreasures.findIndex(i => i.ItemType == ItemType && (i.Sockets || 0) == (Sockets || 0));
@@ -754,7 +762,10 @@ export const addFusionTreasures = (
     });
 };
 
-export const updateChallengeProgress = async (challenges: IUpdateChallengeProgressRequest, accountId: string) => {
+export const updateChallengeProgress = async (
+    challenges: IUpdateChallengeProgressRequest,
+    accountId: string
+): Promise<void> => {
     const inventory = await getInventory(accountId);
 
     addChallenges(inventory, challenges.ChallengeProgress);
@@ -766,7 +777,7 @@ export const updateChallengeProgress = async (challenges: IUpdateChallengeProgre
 export const addSeasonalChallengeHistory = (
     inventory: IInventoryDatabaseDocument,
     itemsArray: ISeasonChallenge[] | undefined
-) => {
+): void => {
     const category = inventory.SeasonChallengeHistory;
 
     itemsArray?.forEach(({ challenge, id }) => {
@@ -780,7 +791,10 @@ export const addSeasonalChallengeHistory = (
     });
 };
 
-export const addChallenges = (inventory: IInventoryDatabaseDocument, itemsArray: IChallengeProgress[] | undefined) => {
+export const addChallenges = (
+    inventory: IInventoryDatabaseDocument,
+    itemsArray: IChallengeProgress[] | undefined
+): void => {
     const category = inventory.ChallengeProgress;
 
     itemsArray?.forEach(({ Name, Progress }) => {
@@ -795,7 +809,7 @@ export const addChallenges = (inventory: IInventoryDatabaseDocument, itemsArray:
     });
 };
 
-const addMissionComplete = (inventory: IInventoryDatabaseDocument, { Tag, Completes }: IMission) => {
+const addMissionComplete = (inventory: IInventoryDatabaseDocument, { Tag, Completes }: IMission): void => {
     const { Missions } = inventory;
     const itemIndex = Missions.findIndex(item => item.Tag === Tag);
 
diff --git a/src/services/loginService.ts b/src/services/loginService.ts
index 80f0b5b6..674b4860 100644
--- a/src/services/loginService.ts
+++ b/src/services/loginService.ts
@@ -34,13 +34,13 @@ export const createAccount = async (accountData: IDatabaseAccount): Promise<IDat
     }
 };
 
-export const createLoadout = async (accountId: Types.ObjectId) => {
+export const createLoadout = async (accountId: Types.ObjectId): Promise<Types.ObjectId> => {
     const loadout = new Loadout({ loadoutOwnerId: accountId });
     const savedLoadout = await loadout.save();
     return savedLoadout._id;
 };
 
-export const createPersonalRooms = async (accountId: Types.ObjectId, shipId: Types.ObjectId) => {
+export const createPersonalRooms = async (accountId: Types.ObjectId, shipId: Types.ObjectId): Promise<void> => {
     const personalRooms = new PersonalRooms({
         ...new_personal_rooms,
         personalRoomsOwnerId: accountId,
diff --git a/src/services/purchaseService.ts b/src/services/purchaseService.ts
index dda15e87..cc09d0f7 100644
--- a/src/services/purchaseService.ts
+++ b/src/services/purchaseService.ts
@@ -25,13 +25,13 @@ import {
     TRarity
 } from "warframe-public-export-plus";
 
-export const getStoreItemCategory = (storeItem: string) => {
+export const getStoreItemCategory = (storeItem: string): string => {
     const storeItemString = getSubstringFromKeyword(storeItem, "StoreItems/");
     const storeItemElements = storeItemString.split("/");
     return storeItemElements[1];
 };
 
-export const getStoreItemTypesCategory = (typesItem: string) => {
+export const getStoreItemTypesCategory = (typesItem: string): string => {
     const typesString = getSubstringFromKeyword(typesItem, "Types");
     const typeElements = typesString.split("/");
     if (typesItem.includes("StoreItems")) {
diff --git a/src/services/recipeService.ts b/src/services/recipeService.ts
index 8594def4..85309273 100644
--- a/src/services/recipeService.ts
+++ b/src/services/recipeService.ts
@@ -4,7 +4,7 @@ import { getRecipe } from "@/src/services/itemDataService";
 import { logger } from "@/src/utils/logger";
 import { Types } from "mongoose";
 
-export const startRecipe = async (recipeName: string, accountId: string) => {
+export const startRecipe = async (recipeName: string, accountId: string): Promise<{ RecipeId: { $oid: string } }> => {
     const recipe = getRecipe(recipeName);
 
     if (!recipe) {
@@ -34,6 +34,6 @@ export const startRecipe = async (recipeName: string, accountId: string) => {
     const newInventory = await inventory.save();
 
     return {
-        RecipeId: { $oid: newInventory.PendingRecipes[newInventory.PendingRecipes.length - 1]._id?.toString() }
+        RecipeId: { $oid: newInventory.PendingRecipes[newInventory.PendingRecipes.length - 1]._id.toString() }
     };
 };
diff --git a/src/utils/logger.ts b/src/utils/logger.ts
index 03aa2562..2ca65ec6 100644
--- a/src/utils/logger.ts
+++ b/src/utils/logger.ts
@@ -103,7 +103,7 @@ export const logger = createLogger({
 
 addColors(logLevels.colors);
 
-export function registerLogFileCreationListener() {
+export function registerLogFileCreationListener(): void {
     errorLog.on("new", filename => logger.info(`Using error log file: ${filename}`));
     combinedLog.on("new", filename => logger.info(`Using combined log file: ${filename}`));
     errorLog.on("rotate", filename => logger.info(`Rotated error log file: ${filename}`));