diff --git a/workbench/backend/src/app/booking/booking.controller.ts b/workbench/backend/src/app/booking/booking.controller.ts
index 45aa739..f8cce01 100644
--- a/workbench/backend/src/app/booking/booking.controller.ts
+++ b/workbench/backend/src/app/booking/booking.controller.ts
@@ -96,7 +96,7 @@ export class BookingController {
           .json({ activityId: e.message });
       }
 
-      let axiosError: AxiosError = e?.error;
+      const axiosError: AxiosError = e?.error;
       return res
         .status(axiosError?.response?.status || 500)
         .json(axiosError?.response?.data);
diff --git a/workbench/backend/src/app/re-optimize/re-optimize.controller.ts b/workbench/backend/src/app/re-optimize/re-optimize.controller.ts
index 2672f60..eb940b5 100644
--- a/workbench/backend/src/app/re-optimize/re-optimize.controller.ts
+++ b/workbench/backend/src/app/re-optimize/re-optimize.controller.ts
@@ -18,7 +18,7 @@ export class ReOptimizeController {
       const { data } = await this.dao.reOptimize('sync', ctx, body).toPromise();
       return res.json(data);
     } catch (e) {
-      let axiosError: AxiosError = e?.error;
+      const axiosError: AxiosError = e?.error;
       return res
         .status(axiosError?.response?.status || 500)
         .json(axiosError?.response?.data);
@@ -30,7 +30,7 @@ export class ReOptimizeController {
       const { data } = await this.dao.reOptimize('async', ctx, body).toPromise();
       return res.json(data);
     } catch (e) {
-      let axiosError: AxiosError = e?.error;
+      const axiosError: AxiosError = e?.error;
       return res
         .status(axiosError?.response?.status || 500)
         .json(axiosError?.response?.data);
diff --git a/workbench/frontend/src/app/common/services/auth.service.ts b/workbench/frontend/src/app/common/services/auth.service.ts
index 725d64d..f09d30c 100644
--- a/workbench/frontend/src/app/common/services/auth.service.ts
+++ b/workbench/frontend/src/app/common/services/auth.service.ts
@@ -27,7 +27,7 @@ const DEFAULT_CTX = {
   selectedLocale: 'en-us',
   user: '<user>',
   userId: 0
-}
+};
 
 @Injectable({
   providedIn: 'root'
@@ -42,14 +42,14 @@ export class AuthService {
 
   public globalContext$ = new BehaviorSubject<GlobalContext>(DEFAULT_CTX);
   public globalContextWithAuth$ = this.globalContext$.pipe(filter((it) => it !== DEFAULT_CTX));
-  public isLoggedIn$ = this.globalContext$.pipe(map(it => it !== DEFAULT_CTX))
+  public isLoggedIn$ = this.globalContext$.pipe(map(it => it !== DEFAULT_CTX));
 
-  public logout() {
+  public logout(): void {
     this.clearContext();
     this.onContextReady(DEFAULT_CTX);
   }
 
-  public openLoginDialog() {
+  public openLoginDialog(): void {
     const dialogRef = this.dialog.open(LoginDialogComponent,
       LoginDialogComponent.CONFIG
     );
@@ -66,14 +66,14 @@ export class AuthService {
     });
   }
 
-  public tryRestoreSession() {
+  public tryRestoreSession(): void {
     const ctx = this.restoreContext();
     if (ctx) {
       this.infoMessage(
         '[✅ INFO ✅] session loaded from sessionStorage',
         'logout', () => this.logout()
       );
-      setTimeout(() => this.onContextReady(ctx), 1)
+      setTimeout(() => this.onContextReady(ctx), 1);
     } else {
       this.infoMessage(
         '[❌ WARN ❌ ] no session found',
@@ -83,18 +83,18 @@ export class AuthService {
     }
   }
 
-  private onContextReady(ctx: GlobalContext) {
+  private onContextReady(ctx: GlobalContext): void {
     this.globalContext$.next(ctx);
   }
 
-  private clearContext() {
+  private clearContext(): void {
     this.infoMessage('[✅ INFO ✅] session cleared from sessionStorage', 'login', () => this.openLoginDialog());
     sessionStorage.removeItem(this.AUTH_KEY);
   }
 
-  private storeContext(ctx: GlobalContext) {
+  private storeContext(ctx: GlobalContext): void {
     this.infoMessage('[✅ INFO ✅] session stored in sessionStorage');
-    sessionStorage.setItem(this.AUTH_KEY, JSON.stringify(ctx))
+    sessionStorage.setItem(this.AUTH_KEY, JSON.stringify(ctx));
   }
 
   private restoreContext(): GlobalContext | null {
@@ -104,7 +104,7 @@ export class AuthService {
       : null;
   }
 
-  private infoMessage(msg: string, btnText = 'ok', action: () => void | null = null) {
+  private infoMessage(msg: string, btnText = 'ok', action: () => void | null = null): void {
     const snackBarRef = this.snackBar.open(msg, btnText, { duration: 5000 });
     if (action) {
       snackBarRef.onAction().subscribe(() => {
diff --git a/workbench/frontend/src/app/common/services/config.service.ts b/workbench/frontend/src/app/common/services/config.service.ts
index 8aedbfa..8f6a342 100644
--- a/workbench/frontend/src/app/common/services/config.service.ts
+++ b/workbench/frontend/src/app/common/services/config.service.ts
@@ -5,14 +5,14 @@ import { Injectable } from '@angular/core';
 export class ConfigService {
   constructor() { }
 
-  private getHost() {
+  private getHost(): 'http://localhost:8000' | '' {
     return location.origin === 'http://localhost:4200'
       ? 'http://localhost:8000'
       : '';
   }
 
-  public getApiUri() {
-    return `${this.getHost()}/api`
+  public getApiUri(): string {
+    return `${this.getHost()}/api`;
   }
 
-}
\ No newline at end of file
+}
diff --git a/workbench/frontend/src/app/common/services/plugin.service.ts b/workbench/frontend/src/app/common/services/plugin.service.ts
index e7227da..79398f4 100644
--- a/workbench/frontend/src/app/common/services/plugin.service.ts
+++ b/workbench/frontend/src/app/common/services/plugin.service.ts
@@ -1,6 +1,6 @@
 import { HttpClient, HttpErrorResponse, HttpHeaders } from '@angular/common/http';
 import { Injectable } from '@angular/core';
-import { of, throwError } from 'rxjs';
+import { Observable, ObservedValueOf, of, throwError } from 'rxjs';
 import { catchError, map, mergeMap } from 'rxjs/operators';
 import { ConfigService } from './config.service';
 import { CLIENT_IDENTIFIER } from '../contants';
@@ -39,10 +39,10 @@ export type PolicyObjectiveDto = {
 })
 export class PluginService {
 
-  private getHeaders(ctx: GlobalContext) {
+  private getHeaders(ctx: GlobalContext): HttpHeaders {
     return new HttpHeaders({
       'Content-Type': 'application/json',
-      'Authorization': `${ctx.authToken}`,
+      Authorization: `${ctx.authToken}`,
       'x-cloud-host': `${ctx.cloudHost}`,
       'x-account-name': `${ctx.account}`,
       'x-account-id': `${ctx.accountId}`,
@@ -70,14 +70,13 @@ export class PluginService {
   }
 
 
-  // tslint:disable-next-line:typedef
-  fetchAll() {
+  fetchAll(): Observable<PluginDto[]> {
     return this.auth.globalContextWithAuth$.pipe(
       mergeMap(ctx => this.http.get<PluginDto[]>(`${this.config.getApiUri()}/plugin`, { headers: this.getHeaders(ctx) })),
     );
   }
 
-  fetchById(id: string) {
+  fetchById(id: string): Observable<ObservedValueOf<Observable<PluginDto>>> {
     return this.auth.globalContextWithAuth$.pipe(
       mergeMap(ctx => this.http.get<PluginDto>(`${this.config.getApiUri()}/plugin/by-id/${id}`, { headers: this.getHeaders(ctx) }))
     );
@@ -91,6 +90,7 @@ export class PluginService {
     );
   }
 
+  // tslint:disable-next-line:typedef
   create(plugin: Partial<PluginDto>) {
     return this.auth.globalContextWithAuth$.pipe(
       mergeMap(ctx => this.http.post<PluginDto>(`${this.config.getApiUri()}/plugin`, plugin, { headers: this.getHeaders(ctx) })),
@@ -106,13 +106,13 @@ export class PluginService {
     );
   }
 
-  update(plugin: Partial<PluginDto>) {
+  update(plugin: Partial<PluginDto>): Observable<ObservedValueOf<Observable<PluginDto>>> {
     return this.auth.globalContextWithAuth$.pipe(
       mergeMap(ctx => this.http.put<PluginDto>(`${this.config.getApiUri()}/plugin/${plugin.id}`, plugin, { headers: this.getHeaders(ctx) }))
     );
   }
 
-  delete(pluginId: string) {
+  delete(pluginId: string): Observable<ObservedValueOf<Observable<PluginDto>>> {
     return this.auth.globalContextWithAuth$.pipe(
       mergeMap(ctx => this.http.delete<PluginDto>(`${this.config.getApiUri()}/plugin/${pluginId}`, { headers: this.getHeaders(ctx) }))
     );
diff --git a/workbench/frontend/src/app/slot-booking/services/booking.service.ts b/workbench/frontend/src/app/slot-booking/services/booking.service.ts
index 7dba6fb..fcaaef3 100644
--- a/workbench/frontend/src/app/slot-booking/services/booking.service.ts
+++ b/workbench/frontend/src/app/slot-booking/services/booking.service.ts
@@ -30,10 +30,10 @@ export class BookingService {
     private query: QueryService
   ) { }
 
-  private getHeaders(ctx: GlobalContext) {
+  private getHeaders(ctx: GlobalContext): HttpHeaders {
     return new HttpHeaders({
       'Content-Type': 'application/json',
-      'Authorization': `${ctx.authToken}`,
+      Authorization: `${ctx.authToken}`,
       'x-cloud-host': `${ctx.cloudHost}`,
       'x-account-name': `${ctx.account}`,
       'x-account-id': `${ctx.accountId}`,
@@ -44,17 +44,19 @@ export class BookingService {
       'x-client-id': CLIENT_IDENTIFIER,
       'x-client-version': '0.0.0',
       'x-request-id': `${Date.now()}`,
-    })
+    });
   }
 
+  // tslint:disable-next-line:typedef
   private book(bookable: SearchResponseItem, job: Job, activityId: string = 'create-activity') {
     return this.auth.globalContextWithAuth$.pipe(
-      mergeMap(ctx => this.http.post<{}>(`${this.config.getApiUri()}/booking/actions/book/${activityId}`, { job, bookable }, { headers: this.getHeaders(ctx) }))
+      mergeMap(ctx => this.http.post<{}>(`${this.config.getApiUri()}/booking/actions/book/${activityId}`,
+        { job, bookable }, { headers: this.getHeaders(ctx) }))
     );
   }
 
 
-  public tryBookAll(list: SearchResponseItem[], job: Job) {
+  public tryBookAll(list: SearchResponseItem[], job: Job): Observable<Progress> {
 
     return new Observable<Progress>((op) => {
 
@@ -68,7 +70,7 @@ export class BookingService {
           current: (idx + 1),
           result: null,
           activityId,
-        }
+        };
 
 
         const person = this.query.getResourceFromCache(bookable.resource);
@@ -83,25 +85,26 @@ export class BookingService {
               success: true,
               message: `🎉🎉 we booked a slot with ${person.firstName} ${person.lastName} from ${moment(bookable.start).format('HH:mm')} to ${moment(bookable.end).format('HH:mm')} `,
               result
-            })
+            });
           })
           .catch(errorRep => {
+            // tslint:disable-next-line:no-shadowed-variable
             let activityId: string;
             // if the backend returns a 422 - creation of temp data was okay but booking failed.
-            // use [activityId] for next try to not recreate data 
+            // use [activityId] for next try to not recreate data
             if (errorRep instanceof HttpErrorResponse && errorRep.status === 422 && errorRep.error) {
-              activityId = errorRep.error.activityId || ''
+              activityId = errorRep.error.activityId || '';
             }
 
             throw { ...progress, activityId: activityId ? activityId : '' };
           });
-      }
+      };
 
-      // setup chain 
+      // setup chain
       const work = list.reduce(
         (promise, it, idx) => promise.catch((progress: Progress) => tryBook(idx, it, progress.blockedList, progress.activityId)),
         Promise.reject({ message: `init`, blockedList: [], success: false, total: list.length, current: -1 })
-      )
+      );
 
       // run chain
       work
@@ -110,15 +113,15 @@ export class BookingService {
           op.complete();
         })
         .catch((error: Progress) => {
-          op.next({ ...error, message: '❌ slot booking failed, all technicains are booked already ...' });
+          op.next({ ...error, message: '❌ slot booking failed, all technicians are booked already ...' });
           op.error(error);
         });
 
       return () => {
-        // clean ups
-      }
-    })
+        // clean-ups
+      };
+    });
 
-  };
+  }
 
-}
\ No newline at end of file
+}
diff --git a/workbench/frontend/src/app/slot-booking/services/job.service.ts b/workbench/frontend/src/app/slot-booking/services/job.service.ts
index 79e8638..1002b3e 100644
--- a/workbench/frontend/src/app/slot-booking/services/job.service.ts
+++ b/workbench/frontend/src/app/slot-booking/services/job.service.ts
@@ -4,6 +4,7 @@ import { mergeMap } from 'rxjs/operators';
 import { ConfigService } from '../../common/services/config.service';
 import { CLIENT_IDENTIFIER } from '../../common/contants';
 import { GlobalContext, AuthService } from '../../common/services/auth.service';
+import { Observable } from 'rxjs';
 
 export type Job = {
   durationMinutes: number,
@@ -13,7 +14,7 @@ export type Job = {
   } | null,
   mandatorySkills: string[],
   optionalSkills: string[]
-}
+};
 
 export type TagDTO = {
   branches: null
@@ -33,7 +34,7 @@ export type TagDTO = {
   syncStatus: 'IN_CLOUD'
   udfMetaGroups: null
   udfValues: null
-}
+};
 
 export type AddressDTO = {
   block: null
@@ -69,16 +70,16 @@ export type AddressDTO = {
   udfMetaGroups: null
   udfValues: null
   zipCode: string
-}
+};
 @Injectable({
   providedIn: 'root'
 })
 export class JobService {
 
-  private getHeaders(ctx: GlobalContext) {
+  private getHeaders(ctx: GlobalContext): HttpHeaders {
     return new HttpHeaders({
       'Content-Type': 'application/json',
-      'Authorization': `${ctx.authToken}`,
+      Authorization: `${ctx.authToken}`,
       'x-cloud-host': `${ctx.cloudHost}`,
       'x-account-name': `${ctx.account}`,
       'x-account-id': `${ctx.accountId}`,
@@ -98,21 +99,24 @@ export class JobService {
     private http: HttpClient,
   ) { }
 
-  fetchAllTags() {
+  fetchAllTags(): Observable<Array<TagDTO & { persons: string[] }>> {
     return this.auth.globalContextWithAuth$.pipe(
-      mergeMap(ctx => this.http.get<Array<TagDTO & { persons: string[] }>>(`${this.config.getApiUri()}/query/tags`, { headers: this.getHeaders(ctx) }))
+      mergeMap(ctx => this.http.get<Array<TagDTO & { persons: string[] }>>(`${this.config.getApiUri()}/query/tags`,
+        { headers: this.getHeaders(ctx) }))
     );
   }
 
-  fetchAllAddress() {
+  fetchAllAddress(): Observable<AddressDTO[]> {
     return this.auth.globalContextWithAuth$.pipe(
-      mergeMap(ctx => this.http.get<AddressDTO[]>(`${this.config.getApiUri()}/query/address`, { headers: this.getHeaders(ctx) })),
+      mergeMap(ctx => this.http.get<AddressDTO[]>(`${this.config.getApiUri()}/query/address`,
+        { headers: this.getHeaders(ctx) })),
     );
   }
 
-  personByTag(tagId: string) {
+  personByTag(tagId: string): Observable<{ person: string; tag: string }[]> {
     return this.auth.globalContextWithAuth$.pipe(
-      mergeMap(ctx => this.http.get<{ person: string, tag: string }[]>(`${this.config.getApiUri()}/query/person/by-tag/${tagId}`, { headers: this.getHeaders(ctx) })),
+      mergeMap(ctx => this.http.get<{ person: string, tag: string }[]>(`${this.config.getApiUri()}/query/person/by-tag/${tagId}`,
+        { headers: this.getHeaders(ctx) })),
     );
   }
 }
diff --git a/workbench/frontend/src/app/slot-booking/services/slot-booking.service.ts b/workbench/frontend/src/app/slot-booking/services/slot-booking.service.ts
index e8a3b6d..28e039f 100644
--- a/workbench/frontend/src/app/slot-booking/services/slot-booking.service.ts
+++ b/workbench/frontend/src/app/slot-booking/services/slot-booking.service.ts
@@ -16,7 +16,7 @@ export type GroupedSearchResponse = {
   hash: string,
   maxScore: number,
   sumScore: number
-}
+};
 
 export type SearchResponseWrapper = SearchResponse & {
   isError: boolean,
@@ -25,9 +25,9 @@ export type SearchResponseWrapper = SearchResponse & {
   grouped: GroupedSearchResponse[]
 };
 
-type SearchResponseItemExteded = SearchResponseItem & {
+type SearchResponseItemExtended = SearchResponseItem & {
   resourceVm: { id: string, firstName: string, lastName: string } | undefined | null
-}
+};
 
 export type SearchResponseItem = {
   slot: { start: string; end: string; },
@@ -39,10 +39,10 @@ export type SearchResponseItem = {
     distanceInMeters: number;
   }
   score: number
-}
+};
 type SearchResponse = {
   results: SearchResponseItem[]
-}
+};
 type ISearchRequestSlot = Readonly<{
   start: string;
   end: string;
@@ -66,11 +66,11 @@ export type SearchRequest = Readonly<{
     maxResultsPerSlot: number;
   }>;
   optimizationPlugin: null | string;
-}>
+}>;
 type ILocation = {
   latitude: number;
   longitude: number;
-}
+};
 
 
 @Injectable({
@@ -78,10 +78,10 @@ type ILocation = {
 })
 export class SlotSearchService {
 
-  private getHeaders(ctx: GlobalContext) {
+  private getHeaders(ctx: GlobalContext): HttpHeaders {
     return new HttpHeaders({
       'Content-Type': 'application/json',
-      'Authorization': `${ctx.authToken}`,
+      Authorization: `${ctx.authToken}`,
       'x-cloud-host': `${ctx.cloudHost}`,
       'x-account-name': `${ctx.account}`,
       'x-account-id': `${ctx.accountId}`,
@@ -92,7 +92,7 @@ export class SlotSearchService {
       'x-client-id': CLIENT_IDENTIFIER,
       'x-client-version': '0.0.0',
       'x-request-id': `${Date.now()}`,
-    })
+    });
   }
 
   constructor(
@@ -108,7 +108,8 @@ export class SlotSearchService {
 
 
     return this.auth.globalContextWithAuth$.pipe(
-      mergeMap(ctx => this.http.post<SearchResponse>(`${this.config.getApiUri()}/job-slots/actions/search`, body, { headers: this.getHeaders(ctx) })),
+      mergeMap(ctx => this.http.post<SearchResponse>(`${this.config.getApiUri()}/job-slots/actions/search`,
+        body, { headers: this.getHeaders(ctx) })),
       map(resp => {
         return {
           ...resp,
@@ -119,7 +120,7 @@ export class SlotSearchService {
 
             const hash = `${it.slot.start}-${it.slot.end}`;
 
-            const extendedItem: SearchResponseItemExteded = {
+            const extendedItem: SearchResponseItemExtended = {
               ...it,
               resourceVm: this.queryService.getResourceFromCache(it.resource)
             };
@@ -128,18 +129,20 @@ export class SlotSearchService {
 
               const group = theMap.get(hash);
               group.items = [...group.items, extendedItem].sort((a, b) => b.score - a.score);
-              group.maxScore = group.maxScore > it.score ? group.maxScore : it.score
+              group.maxScore = group.maxScore > it.score ? group.maxScore : it.score;
               group.sumScore += it.score;
 
             } else {
-              theMap.set(hash, { items: [extendedItem], hash, maxScore: it.score, sumScore: it.score, slot: it.slot })
+              theMap.set(hash, { items: [extendedItem], hash, maxScore: it.score, sumScore: it.score, slot: it.slot });
             }
 
             return theMap;
-          }, new Map<string, { items: SearchResponseItemExteded[], hash: string, maxScore: number, sumScore: number, slot: { start: string; end: string; } }>()))
+          },
+            new Map<string, { items: SearchResponseItemExtended[], hash: string, maxScore: number,
+              sumScore: number, slot: { start: string; end: string; } }>()))
             .map(([, v]) => v)
             .sort((a, b) => b.maxScore - a.maxScore)
-        }
+        };
       })
     );
   }