diff --git a/src/api/admin.ts b/src/api/admin.ts
index 3d2dfc0..45db694 100644
--- a/src/api/admin.ts
+++ b/src/api/admin.ts
@@ -21,19 +21,36 @@ import { BadRequest, Conflict } from 'http-errors'
 import { Database } from '../database'
 import { addPurchase } from '../function/purchase'
 import { getStatusMessage, setStatusMessage } from '../function/statusmessage'
+import { EventHandler } from '../monitoring/eventhandler'
 import { generatePurchaseId } from '../util/token'
 import { WebsocketApi } from '../websocket'
 
-export const createAdminRouter = ({ database, websocket }: {
+export const createAdminRouter = ({ database, websocket, eventHandler }: {
   database: Database
   websocket: WebsocketApi
+  eventHandler: EventHandler
 }) => {
   const router = Router()
 
-  router.get('/status', (_, res) => {
-    res.json({
-      websocketClients: websocket.countConnections()
-    })
+  router.get('/status', async (_, res, next) => {
+    try {
+      res.json({
+        websocketClients: websocket.countConnections(),
+        counters: await eventHandler.getCounters()
+      })
+    } catch (ex) {
+      next(ex)
+    }
+  })
+
+  router.post('/reset-counters', async (_, res, next) => {
+    try {
+      await eventHandler.resetCounters()
+
+      res.json({ ok: true })
+    } catch (ex) {
+      next(ex)
+    }
   })
 
   router.get('/status-message', async (_, res, next) => {
diff --git a/src/api/index.ts b/src/api/index.ts
index adec511..81910d9 100644
--- a/src/api/index.ts
+++ b/src/api/index.ts
@@ -19,6 +19,7 @@ import * as basicAuth from 'basic-auth'
 import * as express from 'express'
 import { VisibleConnectedDevicesManager } from '../connected-devices'
 import { Database } from '../database'
+import { EventHandler } from '../monitoring/eventhandler'
 import { WebsocketApi } from '../websocket'
 import { createAdminRouter } from './admin'
 import { createAuthRouter } from './auth'
@@ -29,10 +30,11 @@ import { createSyncRouter } from './sync'
 
 const adminToken = process.env.ADMIN_TOKEN || ''
 
-export const createApi = ({ database, websocket, connectedDevicesManager }: {
+export const createApi = ({ database, websocket, connectedDevicesManager, eventHandler }: {
   database: Database
   websocket: WebsocketApi
   connectedDevicesManager: VisibleConnectedDevicesManager
+  eventHandler: EventHandler
 }) => {
   const app = express()
 
@@ -48,7 +50,7 @@ export const createApi = ({ database, websocket, connectedDevicesManager }: {
   app.use('/child', createChildRouter({ database, websocket }))
   app.use('/parent', createParentRouter({ database, websocket }))
   app.use('/purchase', createPurchaseRouter({ database, websocket }))
-  app.use('/sync', createSyncRouter({ database, websocket, connectedDevicesManager }))
+  app.use('/sync', createSyncRouter({ database, websocket, connectedDevicesManager, eventHandler }))
 
   app.use(
     '/admin',
@@ -74,7 +76,7 @@ export const createApi = ({ database, websocket, connectedDevicesManager }: {
         res.sendStatus(401)
       }
     },
-    createAdminRouter({ database, websocket })
+    createAdminRouter({ database, websocket, eventHandler })
   )
 
   return app
diff --git a/src/api/sync.ts b/src/api/sync.ts
index 3c89f4d..f2b5423 100644
--- a/src/api/sync.ts
+++ b/src/api/sync.ts
@@ -1,6 +1,6 @@
 /*
  * server component for the TimeLimit App
- * Copyright (C) 2019 Jonas Lochmann
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
@@ -23,6 +23,7 @@ import { Database } from '../database'
 import { reportDeviceRemoved } from '../function/device/report-device-removed'
 import { applyActionsFromDevice } from '../function/sync/apply-actions'
 import { generateServerDataStatus } from '../function/sync/get-server-data-status'
+import { EventHandler } from '../monitoring/eventhandler'
 import { WebsocketApi } from '../websocket'
 import { isClientPullChangesRequest, isClientPushChangesRequest, isRequestWithAuthToken } from './validator'
 
@@ -32,10 +33,11 @@ const getRoundedTimestampForLastConnectivity = () => {
   return now - (now % (1000 * 60 * 60 * 12 /* 12 hours */))
 }
 
-export const createSyncRouter = ({ database, websocket, connectedDevicesManager }: {
+export const createSyncRouter = ({ database, websocket, connectedDevicesManager, eventHandler }: {
   database: Database
   websocket: WebsocketApi
   connectedDevicesManager: VisibleConnectedDevicesManager
+  eventHandler: EventHandler
 }) => {
   const router = Router()
 
@@ -43,7 +45,11 @@ export const createSyncRouter = ({ database, websocket, connectedDevicesManager
     limit: '5120kb'
   }), async (req, res, next) => {
     try {
+      eventHandler.countEvent('pushChangesRequest')
+
       if (!isClientPushChangesRequest(req.body)) {
+        eventHandler.countEvent('pushChangesRequest invalid')
+
         throw new BadRequest()
       }
 
@@ -51,9 +57,14 @@ export const createSyncRouter = ({ database, websocket, connectedDevicesManager
         request: req.body,
         database,
         websocket,
-        connectedDevicesManager
+        connectedDevicesManager,
+        eventHandler
       })
 
+      if (shouldDoFullSync) {
+        eventHandler.countEvent('pushChangesRequest shouldDoFullSync')
+      }
+
       res.json({
         shouldDoFullSync
       })
@@ -64,9 +75,13 @@ export const createSyncRouter = ({ database, websocket, connectedDevicesManager
 
   router.post('/pull-status', json(), async (req, res, next) => {
     try {
+      eventHandler.countEvent('pullStatusRequest')
+
       const { body } = req
 
       if (!isClientPullChangesRequest(body)) {
+        eventHandler.countEvent('pullStatusRequest invalid')
+
         throw new BadRequest()
       }
 
@@ -104,6 +119,14 @@ export const createSyncRouter = ({ database, websocket, connectedDevicesManager
           transaction
         })
 
+        if (serverStatus.devices) { eventHandler.countEvent('pullStatusRequest devices') }
+        if (serverStatus.apps) { eventHandler.countEvent('pullStatusRequest apps') }
+        if (serverStatus.categoryBase) { eventHandler.countEvent('pullStatusRequest categoryBase') }
+        if (serverStatus.categoryApp) { eventHandler.countEvent('pullStatusRequest categoryApp') }
+        if (serverStatus.usedTimes) { eventHandler.countEvent('pullStatusRequest usedTimes') }
+        if (serverStatus.rules) { eventHandler.countEvent('pullStatusRequest rules') }
+        if (serverStatus.users) { eventHandler.countEvent('pullStatusRequest users') }
+
         res.json(serverStatus)
       })
     } catch (ex) {
diff --git a/src/function/sync/apply-actions/index.ts b/src/function/sync/apply-actions/index.ts
index d5ff6df..30683ae 100644
--- a/src/function/sync/apply-actions/index.ts
+++ b/src/function/sync/apply-actions/index.ts
@@ -1,6 +1,6 @@
 /*
  * server component for the TimeLimit App
- * Copyright (C) 2019 Jonas Lochmann
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
@@ -22,6 +22,7 @@ import { ClientPushChangesRequest } from '../../../api/schema'
 import { isSerializedAppLogicAction, isSerializedChildAction, isSerializedParentAction } from '../../../api/validator'
 import { VisibleConnectedDevicesManager } from '../../../connected-devices'
 import { Database } from '../../../database'
+import { EventHandler } from '../../../monitoring/eventhandler'
 import { WebsocketApi } from '../../../websocket'
 import { notifyClientsAboutChanges } from '../../websocket'
 import { Cache } from './cache'
@@ -29,13 +30,18 @@ import { dispatchAppLogicAction } from './dispatch-app-logic-action'
 import { dispatchChildAction } from './dispatch-child-action'
 import { dispatchParentAction } from './dispatch-parent-action'
 
-export const applyActionsFromDevice = async ({ database, request, websocket, connectedDevicesManager }: {
+export const applyActionsFromDevice = async ({ database, request, websocket, connectedDevicesManager, eventHandler }: {
   database: Database
   websocket: WebsocketApi
   request: ClientPushChangesRequest
   connectedDevicesManager: VisibleConnectedDevicesManager
+  eventHandler: EventHandler
 }) => {
+  eventHandler.countEvent('applyActionsFromDevice')
+
   if (request.actions.length > 50) {
+    eventHandler.countEvent('applyActionsFromDevice tooMuchActionsPerRequest')
+
     throw new BadRequest()
   }
 
@@ -90,6 +96,8 @@ export const applyActionsFromDevice = async ({ database, request, websocket, con
       if (action.sequenceNumber < nextSequenceNumber) {
         // action was already received
 
+        eventHandler.countEvent('applyActionsFromDevice sequenceNumberRepeated')
+
         cache.requireFullSync()
         continue
       }
@@ -128,6 +136,8 @@ export const applyActionsFromDevice = async ({ database, request, websocket, con
             const expectedIntegrityValue = createHash('sha512').update(integrityData).digest('hex')
 
             if (action.integrity !== expectedIntegrityValue) {
+              eventHandler.countEvent('applyActionsFromDevice parentActionInvalidIntegrityValue')
+
               throw new Error('invalid integrity value')
             }
           }
@@ -144,6 +154,8 @@ export const applyActionsFromDevice = async ({ database, request, websocket, con
           const expectedIntegrityValue = createHash('sha512').update(integrityData).digest('hex')
 
           if (action.integrity !== expectedIntegrityValue) {
+            eventHandler.countEvent('applyActionsFromDevice childActionInvalidIntegrityValue')
+
             throw new Error('invalid integrity value')
           }
         }
@@ -152,52 +164,86 @@ export const applyActionsFromDevice = async ({ database, request, websocket, con
 
         if (action.type === 'appLogic') {
           if (!isSerializedAppLogicAction(parsedSerializedAction)) {
+            eventHandler.countEvent('applyActionsFromDevice invalidAppLogicAction')
+
             throw new Error('invalid action: ' + action.encodedAction)
           }
 
+          eventHandler.countEvent('applyActionsFromDevice action:' + parsedSerializedAction.type)
+
           const parsedAction = parseAppLogicAction(parsedSerializedAction)
 
-          await dispatchAppLogicAction({
-            action: parsedAction,
-            cache,
-            deviceId: deviceEntry.deviceId
-          })
+          try {
+            await dispatchAppLogicAction({
+              action: parsedAction,
+              cache,
+              deviceId: deviceEntry.deviceId
+            })
+          } catch (ex) {
+            eventHandler.countEvent('applyActionsFromDevice actionWithError:' + parsedSerializedAction.type)
+
+            throw ex
+          }
         } else if (action.type === 'parent') {
           if (!isSerializedParentAction(parsedSerializedAction)) {
+            eventHandler.countEvent('applyActionsFromDevice invalidParentAction')
+
             throw new Error('invalid action' + action.encodedAction)
           }
 
+          eventHandler.countEvent('applyActionsFromDevice action:' + parsedSerializedAction.type)
+
           const parsedAction = parseParentAction(parsedSerializedAction)
 
-          await dispatchParentAction({
-            action: parsedAction,
-            cache,
-            parentUserId: action.userId,
-            sourceDeviceId: deviceEntry.deviceId
-          })
+          try {
+            await dispatchParentAction({
+              action: parsedAction,
+              cache,
+              parentUserId: action.userId,
+              sourceDeviceId: deviceEntry.deviceId
+            })
+          } catch (ex) {
+            eventHandler.countEvent('applyActionsFromDevice actionWithError:' + parsedSerializedAction.type)
+
+            throw ex
+          }
         } else if (action.type === 'child') {
           if (!isSerializedChildAction(parsedSerializedAction)) {
+            eventHandler.countEvent('applyActionsFromDevice invalidChildAction')
+
             throw new Error('invalid action: ' + action.encodedAction)
           }
 
+          eventHandler.countEvent('applyActionsFromDevice action:' + parsedSerializedAction.type)
+
           const parsedAction = parseChildAction(parsedSerializedAction)
 
-          await dispatchChildAction({
-            action: parsedAction,
-            cache,
-            childUserId: action.userId,
-            deviceId: deviceEntry.deviceId
-          })
+          try {
+            await dispatchChildAction({
+              action: parsedAction,
+              cache,
+              childUserId: action.userId,
+              deviceId: deviceEntry.deviceId
+            })
+          } catch (ex) {
+            eventHandler.countEvent('applyActionsFromDevice actionWithError:' + parsedSerializedAction.type)
+
+            throw ex
+          }
         } else {
           throw new Error('illegal state')
         }
       } catch (ex) {
+        eventHandler.countEvent('applyActionsFromDevice errorDispatchingAction')
+
         cache.requireFullSync()
       }
     }
 
     // save new next sequence number
     if (nextSequenceNumber !== deviceEntry.nextSequenceNumber) {
+      eventHandler.countEvent('applyActionsFromDevice updateSequenceNumber')
+
       await database.device.update({
         nextSequenceNumber
       }, {
@@ -219,6 +265,10 @@ export const applyActionsFromDevice = async ({ database, request, websocket, con
     }
   })
 
+  if (areChangesImportant) {
+    eventHandler.countEvent('applyActionsFromDevice areChangesImportant')
+  }
+
   await notifyClientsAboutChanges({
     familyId,
     sourceDeviceId,
diff --git a/src/index.ts b/src/index.ts
index 625d11e..0634072 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -19,12 +19,15 @@ import { Server } from 'http'
 import { createApi } from './api'
 import { VisibleConnectedDevicesManager } from './connected-devices'
 import { defaultDatabase, defaultUmzug } from './database'
+import { EventHandler } from './monitoring/eventhandler'
+import { InMemoryEventHandler } from './monitoring/inmemoryeventhandler'
 import { createWebsocketHandler } from './websocket'
 import { initWorkers } from './worker'
 
 async function main () {
   await defaultUmzug.up()
   const database = defaultDatabase
+  const eventHandler: EventHandler = new InMemoryEventHandler()
 
   const connectedDevicesManager = new VisibleConnectedDevicesManager({
     database
@@ -43,7 +46,8 @@ async function main () {
   const api = createApi({
     database,
     websocket: websocketApi,
-    connectedDevicesManager
+    connectedDevicesManager,
+    eventHandler
   })
 
   const server = new Server(api)
diff --git a/src/monitoring/eventhandler.ts b/src/monitoring/eventhandler.ts
new file mode 100644
index 0000000..80b1acd
--- /dev/null
+++ b/src/monitoring/eventhandler.ts
@@ -0,0 +1,22 @@
+/*
+ * server component for the TimeLimit App
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+export interface EventHandler {
+  countEvent (name: string): void
+  getCounters (): Promise<{[key: string]: number}>
+  resetCounters (): Promise<void>
+}
diff --git a/src/monitoring/inmemoryeventhandler.ts b/src/monitoring/inmemoryeventhandler.ts
new file mode 100644
index 0000000..86d3edc
--- /dev/null
+++ b/src/monitoring/inmemoryeventhandler.ts
@@ -0,0 +1,43 @@
+/*
+ * server component for the TimeLimit App
+ * Copyright (C) 2019 - 2020 Jonas Lochmann
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import { EventHandler } from './eventhandler'
+
+export class InMemoryEventHandler implements EventHandler {
+  private counters = new Map<string, number>()
+
+  countEvent (name: string) {
+    this.counters.set(
+      name,
+      (this.counters.get(name) || 0) + 1
+    )
+  }
+
+  async getCounters () {
+    const result: {[key: string]: number} = {}
+
+    this.counters.forEach((value, key) => {
+      result[key] = value
+    })
+
+    return result
+  }
+
+  async resetCounters () {
+    this.counters.clear()
+  }
+}