diff --git a/server/logger.test.ts b/server/logger.test.ts
index d3c946c..db93643 100644
--- a/server/logger.test.ts
+++ b/server/logger.test.ts
@@ -1,6 +1,5 @@
-import {LogLevel, LogLevels, isLogLevel} from "./types";
+import {isLogLevel, LogLevel, LogLevels} from "./types";
 import {ActivatableLoggerImpl} from "./logger";
-import _ from "lodash";
 
 class TestableLogger extends ActivatableLoggerImpl {
     private logs: any[][] = [];
@@ -35,13 +34,13 @@ function parseLogEntry(logEntry: any[]): ParsedLogEntry {
             `Empty log entry. Should always start with log message: ${logEntry}`
         );
     }
-    
+
     const logMessage = logEntry[0];
     if (typeof logMessage !== "string") {
         throw new Error(
             `Expected log entry to start with string, but got: ${logMessage}`
         );
-    } 
+    }
 
     const regexp = /^\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2} ([A-Z]+) - (\[[^\]]*\])? *(.*)$/;
     const groups = logMessage.match(regexp);
@@ -59,13 +58,13 @@ function parseLogEntry(logEntry: any[]): ParsedLogEntry {
     }
 
     const tagsStr = groups[2].substring(1, groups[2].length - 1);
-    const tags = tagsStr ? _.split(tagsStr, ", ") : [];
+    const tags = tagsStr ? tagsStr.split(", "): [];
     const message = groups[3];
     const args = logEntry.slice(1);
 
     return {
         level: level as LogLevel,
-        tags, 
+        tags,
         message,
         args,
     };
@@ -158,7 +157,7 @@ for (const level of LogLevels) {
             message: "%s %d %f %o %%",
             args: [],
         }]);
-    }); 
+    });
 
     test(`should not escape ${level} message arguments`, () => {
         // given
@@ -174,7 +173,7 @@ for (const level of LogLevels) {
             message: "message",
             args: [1, "%s", "%d", "%f", "%o", "%"],
         }]);
-    }); 
+    });
 
     test(`should not log ${level} message on disabled logger`, () => {
         // given
@@ -185,6 +184,6 @@ for (const level of LogLevels) {
 
         // then
         expect(parseLogs(logger.getLogs())).toEqual([]);
-    }); 
+    });
 }
 
diff --git a/server/logger.ts b/server/logger.ts
index edaadc7..f787c8a 100644
--- a/server/logger.ts
+++ b/server/logger.ts
@@ -1,6 +1,5 @@
-import {Logger, TaggedLogger, LogLevel} from './types';
+import {isString, Logger, LogLevel, TaggedLogger} from './types';
 import moment from 'moment';
-import _ from 'lodash';
 
 export type LoggingFunction = (...args: any[]) => void;
 
@@ -36,15 +35,15 @@ export class ActivatableLoggerImpl implements ActivatableLogger {
                 log(level: LogLevel, ...args: any[]): void {
                     const timeStr = moment().format('YYYY-MM-DD HH:mm:ss');
                     const levelStr = level.toUpperCase();
-                    const tagsStr = tags ? '[' + _.join(tags, ', ') + ']' : '';
+                    const tagsStr = tags ? '[' + tags.join(', ') + ']' : '';
                     const messagePrefix = `${timeStr} ${levelStr} - ${tagsStr}`;
 
                     // Make sure to only replace %s, etc. in real log message
                     // but not in tags.
                     const escapedMessagePrefix = messagePrefix.replace(/%/g, '%%');
-                    
+
                     let message = '';
-                    if (args && _.isString(args[0])) {
+                    if (args && isString(args[0])) {
                         message = args[0];
                         args.shift();
                     }
diff --git a/server/resources/monitoringResource.ts b/server/resources/monitoringResource.ts
index ec54a3f..4b44c0c 100644
--- a/server/resources/monitoringResource.ts
+++ b/server/resources/monitoringResource.ts
@@ -1,5 +1,3 @@
-import _ from "lodash";
-
 import CONSTRAINTS from "../validation/constraints";
 import ErrorTypes from "../utils/errorTypes";
 import * as MonitoringService from "../services/monitoringService";
@@ -17,8 +15,8 @@ async function doGetAll(req: Request): Promise<{ total: number, result: any }> {
     const {monitoringStates, total} = await MonitoringService.getAll(restParams);
     return {
         total,
-        result: _.map(monitoringStates, function (state) {
-            state.mapId = _.toLower(state.mac).replace(/:/g, '');
+        result: monitoringStates.map(state => {
+            state.mapId = state.mac.toLowerCase().replace(/:/g, "");
             return state;
         })
     };
diff --git a/server/resources/nodeResource.ts b/server/resources/nodeResource.ts
index 92d9d14..afb754a 100644
--- a/server/resources/nodeResource.ts
+++ b/server/resources/nodeResource.ts
@@ -1,5 +1,3 @@
-import _ from "lodash";
-
 import Constraints from "../validation/constraints";
 import ErrorTypes from "../utils/errorTypes";
 import * as MonitoringService from "../services/monitoringService";
@@ -13,12 +11,12 @@ import {
     CreateOrUpdateNode,
     DomainSpecificNodeResponse,
     isNodeSortField,
-    isToken, JSONObject,
+    isToken,
+    JSONObject,
     MAC,
     NodeResponse,
     NodeStateData,
     NodeTokenResponse,
-    StoredNode,
     toDomainSpecificNodeResponse,
     Token,
     toNodeResponse,
@@ -27,15 +25,18 @@ import {
 
 const nodeFields = ['hostname', 'key', 'email', 'nickname', 'mac', 'coords', 'monitoring'];
 
+// TODO: Rename
 function getNormalizedNodeData(reqData: any): CreateOrUpdateNode {
     const node: { [key: string]: any } = {};
-    _.each(nodeFields, function (field) {
+    for (const field of nodeFields) {
         let value = normalizeString(reqData[field]);
         if (field === 'mac') {
             value = normalizeMac(value as MAC);
         }
         node[field] = value;
-    });
+    }
+
+    // TODO: Add typeguard before cast.
     return node as CreateOrUpdateNode;
 }
 
@@ -90,15 +91,15 @@ async function doGetAll(req: Request): Promise<{ total: number; pageNodes: any }
 
     const nodes = await NodeService.getAllNodes();
 
-    const realNodes = _.filter(nodes, node =>
+    const realNodes = nodes.filter(node =>
         // We ignore nodes without tokens as those are only manually added ones like gateways.
-        !!node.token
+        !!node.token // FIXME: As node.token may not be undefined or null here, handle this when loading!
     );
 
-    const macs: MAC[] = _.map(realNodes, (node: StoredNode): MAC => node.mac);
+    const macs: MAC[] = realNodes.map(node => node.mac);
     const nodeStateByMac = await MonitoringService.getByMacs(macs);
 
-    const domainSpecificNodes: DomainSpecificNodeResponse[] = _.map(realNodes, (node: StoredNode): DomainSpecificNodeResponse => {
+    const domainSpecificNodes: DomainSpecificNodeResponse[] = realNodes.map(node => {
         const nodeState: NodeStateData = nodeStateByMac[node.mac] || {};
         return toDomainSpecificNodeResponse(node, nodeState);
     });
diff --git a/server/resources/taskResource.ts b/server/resources/taskResource.ts
index e598bcb..6020d05 100644
--- a/server/resources/taskResource.ts
+++ b/server/resources/taskResource.ts
@@ -1,9 +1,7 @@
-import _ from "lodash";
-
 import CONSTRAINTS from "../validation/constraints";
 import ErrorTypes from "../utils/errorTypes";
 import * as Resources from "../utils/resources";
-import {Entity, handleJSONWithData, RequestData} from "../utils/resources";
+import {handleJSONWithData, RequestData} from "../utils/resources";
 import {getTasks, Task, TaskState} from "../jobs/scheduler";
 import {normalizeString} from "../utils/strings";
 import {forConstraint} from "../validation/validator";
@@ -77,11 +75,11 @@ async function setTaskEnabled(data: RequestData, enable: boolean): Promise<TaskR
     return toTaskResponse(task);
 }
 
-async function doGetAll(req: Request): Promise<{ total: number, pageTasks: Entity[] }> {
+async function doGetAll(req: Request): Promise<{ total: number, pageTasks: Task[] }> {
     const restParams = await Resources.getValidRestParams('list', null, req);
 
     const tasks = Resources.sort(
-        _.values(getTasks()),
+        Object.values(getTasks()),
         isTaskSortField,
         restParams
     );
@@ -104,7 +102,7 @@ export function getAll(req: Request, res: Response): void {
     doGetAll(req)
         .then(({total, pageTasks}) => {
             res.set('X-Total-Count', total.toString(10));
-            Resources.success(res, _.map(pageTasks, toTaskResponse));
+            Resources.success(res, pageTasks.map(toTaskResponse));
         })
         .catch(err => Resources.error(res, err));
 }
diff --git a/server/services/mailService.ts b/server/services/mailService.ts
index 1068375..1060c62 100644
--- a/server/services/mailService.ts
+++ b/server/services/mailService.ts
@@ -170,7 +170,7 @@ export async function getPendingMails(restParams: RestParams): Promise<{ mails:
 
     const mails = await db.all(
         'SELECT * FROM email_queue WHERE ' + filter.query,
-        _.concat([], filter.params),
+        filter.params,
     );
 
     return {
diff --git a/server/services/mailTemplateService.ts b/server/services/mailTemplateService.ts
index e9c617f..d2289c4 100644
--- a/server/services/mailTemplateService.ts
+++ b/server/services/mailTemplateService.ts
@@ -97,7 +97,7 @@ export async function render(mailOptions: Mail): Promise<{subject: string, body:
 
     try {
         return {
-            subject: _.trim(_.template(subject.toString())(data)),
+            subject: _.template(subject.toString())(data).trim(),
             body: _.template(body.toString())(data)
         };
     } catch (error) {
diff --git a/server/services/monitoringService.ts b/server/services/monitoringService.ts
index 65d0a37..5f6c2d5 100644
--- a/server/services/monitoringService.ts
+++ b/server/services/monitoringService.ts
@@ -19,10 +19,13 @@ import {
     Domain,
     DurationSeconds,
     Hostname,
+    isBoolean,
     isDomain,
     isMonitoringSortField,
     isOnlineState,
     isSite,
+    isString,
+    isUndefined,
     MAC,
     MailType,
     MonitoringSortField,
@@ -164,7 +167,7 @@ async function storeNodeInformation(nodeData: ParsedNode, node: StoredNode): Pro
 
     const row = await db.get('SELECT * FROM node_state WHERE mac = ?', [node.mac]);
 
-    if (_.isUndefined(row)) {
+    if (isUndefined(row)) {
         return await insertNodeInformation(nodeData, node);
     } else {
         return await updateNodeInformation(nodeData, node, row);
@@ -188,7 +191,7 @@ export function parseNode(importTimestamp: UnixTimestampSeconds, nodeData: any):
     }
 
     const nodeId = nodeData.nodeinfo.node_id;
-    if (!nodeId || !_.isString(nodeId)) {
+    if (!nodeId || !isString(nodeId)) {
         throw new Error(
             `Invalid node id of type "${typeof nodeId}": ${nodeId}`
         );
@@ -212,7 +215,7 @@ export function parseNode(importTimestamp: UnixTimestampSeconds, nodeData: any):
             'Node ' + nodeId + ': Unexpected flags type: ' + (typeof nodeData.flags)
         );
     }
-    if (!_.isBoolean(nodeData.flags.online)) {
+    if (!isBoolean(nodeData.flags.online)) {
         throw new Error(
             'Node ' + nodeId + ': Unexpected flags.online type: ' + (typeof nodeData.flags.online)
         );
@@ -558,6 +561,7 @@ async function retrieveNodeInformationForUrls(urls: string[]): Promise<RetrieveN
     }
 }
 
+// FIXME: Replace any[] by type.
 export async function getAll(restParams: RestParams): Promise<{ total: number, monitoringStates: any[] }> {
     const filterFields = [
         'hostname',
@@ -571,7 +575,7 @@ export async function getAll(restParams: RestParams): Promise<{ total: number, m
 
     const row = await db.get<{ total: number }>(
         'SELECT count(*) AS total FROM node_state WHERE ' + where.query,
-        _.concat([], where.params),
+        where.params,
     );
 
     const total = row?.total || 0;
@@ -585,7 +589,7 @@ export async function getAll(restParams: RestParams): Promise<{ total: number, m
 
     const monitoringStates = await db.all(
         'SELECT * FROM node_state WHERE ' + filter.query,
-        _.concat([], filter.params),
+        filter.params,
     );
 
     return {monitoringStates, total};
@@ -603,7 +607,7 @@ export async function getByMacs(macs: MAC[]): Promise<Record<MAC, NodeStateData>
 
         const rows = await db.all<NodeStateRow>(
             'SELECT * FROM node_state WHERE ' + inCondition.query,
-            _.concat([], inCondition.params),
+            inCondition.params,
         );
 
         for (const row of rows) {
@@ -734,7 +738,7 @@ async function deleteNeverOnlineNodesBefore(deleteBefore: UnixTimestampSeconds):
             deletionCandidates.length
         );
 
-    const deletionCandidateMacs: MAC[] = _.map(deletionCandidates, node => node.mac);
+    const deletionCandidateMacs: MAC[] = deletionCandidates.map(node => node.mac);
     const chunks: MAC[][] = _.chunk(deletionCandidateMacs, NEVER_ONLINE_NODES_DELETION_CHUNK_SIZE);
 
     Logger
@@ -753,10 +757,7 @@ async function deleteNeverOnlineNodesBefore(deleteBefore: UnixTimestampSeconds):
                 ' MACs for deletion.'
             );
 
-        const placeholders = _.join(
-            _.map(macs, () => '?'),
-            ','
-        );
+        const placeholders = macs.map(() => '?').join(',');
 
         const rows: { mac: MAC }[] = await db.all(
             `SELECT * FROM node_state WHERE mac IN (${placeholders})`,
@@ -773,7 +774,7 @@ async function deleteNeverOnlineNodesBefore(deleteBefore: UnixTimestampSeconds):
                 ' nodes found in monitoring database. Those should be skipped.'
             );
 
-        const seenMacs: MAC[] = _.map(rows, (row: { mac: MAC }) => row.mac as MAC);
+        const seenMacs: MAC[] = rows.map(row => row.mac);
         const neverSeenMacs = _.difference(macs, seenMacs);
 
         Logger
diff --git a/server/services/nodeService.ts b/server/services/nodeService.ts
index 8807f8d..7a12def 100644
--- a/server/services/nodeService.ts
+++ b/server/services/nodeService.ts
@@ -108,15 +108,15 @@ async function findFilesInPeersPath(): Promise<string[]> {
 }
 
 function parseNodeFilename(filename: string): NodeFilenameParsed {
-    const parts = _.split(filename, '@', filenameParts.length);
+    const parts = filename.split('@', filenameParts.length);
     const parsed: { [key: string]: string | undefined } = {};
     const zippedParts = _.zip<string, string>(filenameParts, parts);
-    _.each(zippedParts, part => {
+    for (const part of zippedParts) {
         const key = part[0];
         if (key) {
             parsed[key] = part[1];
         }
-    });
+    }
     return parsed;
 }
 
@@ -565,14 +565,14 @@ export async function fixNodeFilenames(): Promise<void> {
 
 export async function findNodesModifiedBefore(timestamp: UnixTimestampSeconds): Promise<StoredNode[]> {
     const nodes = await getAllNodes();
-    return _.filter(nodes, node => node.modifiedAt < timestamp);
+    return nodes.filter(node => node.modifiedAt < timestamp);
 }
 
 export async function getNodeStatistics(): Promise<NodeStatistics> {
     const nodes = await getAllNodes();
 
     const nodeStatistics: NodeStatistics = {
-        registered: _.size(nodes),
+        registered: nodes.length,
         withVPN: 0,
         withCoords: 0,
         monitoring: {
diff --git a/server/types/shared.ts b/server/types/shared.ts
index 62c1a58..e1b31e0 100644
--- a/server/types/shared.ts
+++ b/server/types/shared.ts
@@ -116,6 +116,10 @@ export function toIsEnum<E>(enumDef: E): EnumTypeGuard<E> {
     return (arg): arg is EnumValue<E> => Object.values(enumDef).includes(arg as [keyof E]);
 }
 
+export function isRegExp(arg: unknown): arg is RegExp {
+    return isObject(arg) && arg instanceof RegExp;
+}
+
 export function isOptional<T>(arg: unknown, isT: TypeGuard<T>): arg is (T | undefined) {
     return arg === undefined || isT(arg);
 }
diff --git a/server/utils/databaseUtil.ts b/server/utils/databaseUtil.ts
index 0865577..aad4b66 100644
--- a/server/utils/databaseUtil.ts
+++ b/server/utils/databaseUtil.ts
@@ -2,7 +2,7 @@ import _ from "lodash";
 
 export function inCondition<T>(field: string, list: T[]): {query: string, params: T[]} {
     return {
-        query: '(' + field + ' IN (' + _.join(_.times(list.length, _.constant('?')), ', ') + '))',
+        query: '(' + field + ' IN (' + _.times(list.length, () =>'?').join(', ') + '))',
         params: list,
     }
 }
diff --git a/server/utils/resources.ts b/server/utils/resources.ts
index 94722fc..3d459c5 100644
--- a/server/utils/resources.ts
+++ b/server/utils/resources.ts
@@ -184,7 +184,7 @@ export function filter<E>(entities: E[], allowedFilterFields: string[], restPara
         if (!query) {
             return true;
         }
-        return _.some(allowedFilterFields, (field: string): boolean => {
+        return allowedFilterFields.some((field: string): boolean => {
             if (!query) {
                 return true;
             }
@@ -209,15 +209,15 @@ export function filter<E>(entities: E[], allowedFilterFields: string[], restPara
     const filters = restParams.filters;
 
     function filtersMatch(entity: Entity): boolean {
-        if (_.isEmpty(filters)) {
+        if (isUndefined(filters) || _.isEmpty(filters)) {
             return true;
         }
 
-        return _.every(filters, (value: any, key: string): boolean => {
+        return Object.entries(filters).every(([key, value]) => {
             if (isUndefined(value)) {
                 return true;
             }
-            if (_.startsWith(key, 'has')) {
+            if (key.startsWith('has')) {
                 const entityKey = key.substring(3, 4).toLowerCase() + key.substring(4);
                 return _.isEmpty(entity[entityKey]).toString() !== value;
             }
@@ -225,9 +225,7 @@ export function filter<E>(entities: E[], allowedFilterFields: string[], restPara
         });
     }
 
-    return _.filter(entities, function (entity) {
-        return queryMatches(entity) && filtersMatch(entity);
-    });
+    return entities.filter(entity => queryMatches(entity) && filtersMatch(entity));
 }
 
 export function sort<T extends Record<S, any>, S extends string>(entities: T[], isSortField: TypeGuard<S>, restParams: RestParams): T[] {
@@ -262,7 +260,7 @@ export function sort<T extends Record<S, any>, S extends string>(entities: T[],
     return sorted;
 }
 
-export function getPageEntities(entities: Entity[], restParams: RestParams) {
+export function getPageEntities<Entity>(entities: Entity[], restParams: RestParams): Entity[] {
     const page = restParams._page;
     const perPage = restParams._perPage;
 
@@ -291,7 +289,7 @@ export function filterClause<S>(
 
     return {
         query: filter.query + ' ' + orderBy.query + ' ' + limitOffset.query,
-        params: _.concat(filter.params, orderBy.params, limitOffset.params)
+        params: [...filter.params, ...orderBy.params, ...limitOffset.params]
     };
 }
 
diff --git a/server/utils/strings.ts b/server/utils/strings.ts
index 12ba84d..b19f155 100644
--- a/server/utils/strings.ts
+++ b/server/utils/strings.ts
@@ -1,8 +1,8 @@
 import _ from "lodash"
-import {MAC} from "../types";
+import {isString, MAC} from "../types";
 
 export function normalizeString(str: string): string {
-    return _.isString(str) ? str.trim().replace(/\s+/g, ' ') : str;
+    return isString(str) ? str.trim().replace(/\s+/g, ' ') : str;
 }
 
 export function normalizeMac(mac: MAC): MAC {
diff --git a/server/utils/time.ts b/server/utils/time.ts
index 2dd4a42..83bcdf8 100644
--- a/server/utils/time.ts
+++ b/server/utils/time.ts
@@ -1,5 +1,4 @@
-import {DurationSeconds, UnixTimestampSeconds} from "../types";
-import _ from "lodash";
+import {DurationSeconds, isString, UnixTimestampSeconds} from "../types";
 import moment, {Moment} from "moment";
 
 export function now(): UnixTimestampSeconds {
@@ -45,7 +44,7 @@ export function formatTimestamp(timestamp: UnixTimestampSeconds): string {
 }
 
 export function parseTimestamp(timestamp: any): UnixTimestampSeconds | null {
-    if (!_.isString(timestamp)) {
+    if (!isString(timestamp)) {
         return null;
     }
     const parsed = moment.utc(timestamp);
diff --git a/server/utils/urlBuilder.ts b/server/utils/urlBuilder.ts
index 79b037e..384537c 100644
--- a/server/utils/urlBuilder.ts
+++ b/server/utils/urlBuilder.ts
@@ -1,4 +1,3 @@
-import _ from "lodash"
 import {config} from "../config"
 import {MonitoringToken, Url} from "../types"
 
@@ -12,15 +11,10 @@ function formUrl(route: string, queryParams?: { [key: string]: string }): Url {
     }
     if (queryParams) {
         url += '?';
-        url += _.join(
-            _.map(
-                queryParams,
-                function (value, key) {
-                    return encodeURIComponent(key) + '=' + encodeURIComponent(value);
-                }
-            ),
-            '&'
-        );
+        url +=
+            Object.entries(queryParams)
+                .map(([key, value]) => encodeURIComponent(key) + '=' + encodeURIComponent(value))
+                .join("&");
     }
     return url as Url;
 }
diff --git a/server/validation/validator.ts b/server/validation/validator.ts
index 1879f0e..523ac14 100644
--- a/server/validation/validator.ts
+++ b/server/validation/validator.ts
@@ -1,7 +1,6 @@
-import _ from "lodash";
-
 import {parseInteger} from "../utils/strings";
 import Logger from "../logger";
+import {isArray, isBoolean, isNumber, isObject, isRegExp, isString, isUndefined} from "../types";
 
 export interface Constraint {
     type: string,
@@ -18,52 +17,48 @@ export interface Constraint {
     regex?: RegExp,
 }
 
-export type Constraints = {[key: string]: Constraint};
-export type Values = {[key: string]: any};
-
-function isStringArray(arr: any): arr is string[] {
-    return _.isArray(arr) && _.every(arr, (val: any) => _.isString(val));
-}
+export type Constraints = { [key: string]: Constraint };
+export type Values = { [key: string]: any };
 
 export function isConstraint(val: any): val is Constraint {
-    if (!_.isObject(val)) {
+    if (!isObject(val)) {
         return false;
     }
 
-    const constraint = val as {[key: string]: any};
+    const constraint = val as { [key: string]: any };
 
-    if (!("type" in constraint) || !_.isString(constraint.type)) {
+    if (!("type" in constraint) || !isString(constraint.type)) {
         return false;
     }
 
     if ("optional" in constraint
-        && !_.isUndefined(constraint.optional)
-        && !_.isBoolean(constraint.optional)) {
+        && !isUndefined(constraint.optional)
+        && !isBoolean(constraint.optional)) {
         return false;
     }
 
     if ("allowed" in constraint
-        && !_.isUndefined(constraint.allowed)
-        && !isStringArray(constraint.allowed)) {
+        && !isUndefined(constraint.allowed)
+        && !isArray(constraint.allowed, isString)) {
         return false;
     }
 
     if ("min" in constraint
-        && !_.isUndefined(constraint.min)
-        && !_.isNumber(constraint.min)) {
+        && !isUndefined(constraint.min)
+        && !isNumber(constraint.min)) {
         return false;
     }
 
     if ("max" in constraint
-        && !_.isUndefined(constraint.max)
-        && !_.isNumber(constraint.max)) {
+        && !isUndefined(constraint.max)
+        && !isNumber(constraint.max)) {
         return false;
     }
 
     // noinspection RedundantIfStatementJS
     if ("regex" in constraint
-        && !_.isUndefined(constraint.regex)
-        && !_.isRegExp(constraint.regex)) {
+        && !isUndefined(constraint.regex)
+        && !isRegExp(constraint.regex)) {
         return false;
     }
 
@@ -71,41 +66,38 @@ export function isConstraint(val: any): val is Constraint {
 }
 
 export function isConstraints(constraints: any): constraints is Constraints {
-    if (!_.isObject(constraints)) {
+    if (!isObject(constraints)) {
         return false;
     }
 
-    return _.every(
-        constraints,
-        (constraint: any, key: any) => _.isString(key) && isConstraint(constraint)
-    );
+    return Object.entries(constraints).every(([key, constraint]) => isString(key) && isConstraint(constraint));
 }
 
 // TODO: sanitize input for further processing as specified by constraints (correct types, trimming, etc.)
 
 function isValidBoolean(value: any): boolean {
-    return _.isBoolean(value) || value === 'true' || value === 'false';
+    return isBoolean(value) || value === 'true' || value === 'false';
 }
 
 function isValidNumber(constraint: Constraint, value: any): boolean {
-    if (_.isString(value)) {
+    if (isString(value)) {
         value = parseInteger(value);
     }
 
-    if (!_.isNumber(value)) {
+    if (!isNumber(value)) {
         return false;
     }
 
-    if (_.isNaN(value) || !_.isFinite(value)) {
+    if (isNaN(value) || !isFinite(value)) {
         return false;
     }
 
-    if (_.isNumber(constraint.min) && value < constraint.min) {
+    if (isNumber(constraint.min) && value < constraint.min) {
         return false;
     }
 
     // noinspection RedundantIfStatementJS
-    if (_.isNumber(constraint.max) && value > constraint.max) {
+    if (isNumber(constraint.max) && value > constraint.max) {
         return false;
     }
 
@@ -113,11 +105,12 @@ function isValidNumber(constraint: Constraint, value: any): boolean {
 }
 
 function isValidEnum(constraint: Constraint, value: any): boolean {
-    if (!_.isString(value)) {
+    if (!isString(value)) {
         return false;
     }
 
-    return _.indexOf(constraint.allowed, value) >= 0;
+    const allowed = constraint.allowed || [];
+    return allowed.indexOf(value) >= 0;
 }
 
 function isValidString(constraint: Constraint, value: any): boolean {
@@ -125,7 +118,7 @@ function isValidString(constraint: Constraint, value: any): boolean {
         throw new Error("String constraints must have regex set: " + constraint);
     }
 
-    if (!_.isString(value)) {
+    if (!isString(value)) {
         return false;
     }
 
@@ -174,10 +167,10 @@ function areValid(constraints: Constraints, acceptUndefined: boolean, values: Va
     return true;
 }
 
-export function forConstraint (constraint: Constraint, acceptUndefined: boolean): (value: any) => boolean {
+export function forConstraint(constraint: Constraint, acceptUndefined: boolean): (value: any) => boolean {
     return ((value: any): boolean => isValid(constraint, acceptUndefined, value));
 }
 
-export function forConstraints (constraints: Constraints, acceptUndefined: boolean): (values: Values) => boolean {
+export function forConstraints(constraints: Constraints, acceptUndefined: boolean): (values: Values) => boolean {
     return ((values: Values): boolean => areValid(constraints, acceptUndefined, values));
 }