diff --git a/server/src/routes/analytic_units_router.ts b/server/src/routes/analytic_units_router.ts
index 03bbc12..7fbf283 100644
--- a/server/src/routes/analytic_units_router.ts
+++ b/server/src/routes/analytic_units_router.ts
@@ -13,6 +13,9 @@ async function getStatus(ctx: Router.IRouterContext) {
     }
 
     let analyticUnit = await AnalyticUnit.findById(analyticUnitId);
+    if(analyticUnit === null) {
+      throw new Error(`Cannot find analytic unit with id ${analyticUnitId}`);
+    }
 
     ctx.response.body = {
       status: analyticUnit.status
@@ -24,19 +27,24 @@ async function getStatus(ctx: Router.IRouterContext) {
   } catch(e) {
     console.error(e);
     ctx.response.status = 404;
-    ctx.response.body = 'Can`t find anything';
+    ctx.response.body = {
+      code: 404,
+      message: `GET /analyticUnits/status error: ${e.message}`
+    };
   }
 }
 
 async function getUnit(ctx: Router.IRouterContext) {
   try {
     let analyticUnitId = ctx.request.query.id;
-
     if(analyticUnitId === undefined) {
       throw new Error('No id param in query');
     }
 
     let analyticUnit = await AnalyticUnit.findById(analyticUnitId);
+    if(analyticUnit === null) {
+      throw new Error(`Cannot find analytic unit with id ${analyticUnitId}`);
+    }
 
     ctx.response.body = {
       name: analyticUnit.name,
@@ -46,9 +54,11 @@ async function getUnit(ctx: Router.IRouterContext) {
 
   } catch(e) {
     console.error(e);
-    // TODO: better send 404 when we know than isn`t found
-    ctx.response.status = 500;
-    ctx.response.body = 'Can`t find anything';
+    ctx.response.status = 404;
+    ctx.response.body = {
+      code: 404,
+      message: `GET /analyticUnits error: ${e.message}`
+    };
   }
 }
 
@@ -60,7 +70,7 @@ async function createUnit(ctx: Router.IRouterContext) {
     ctx.response.status = 500;
     ctx.response.body = {
       code: 500,
-      message: `Creation error: ${e.message}`
+      message: `POST /analyticUnits error: ${e.message}`
     };
   }
 
@@ -68,16 +78,21 @@ async function createUnit(ctx: Router.IRouterContext) {
 
 async function deleteUnit(ctx: Router.IRouterContext) {
   try {
-    await AnalyticUnit.remove(ctx.request.query.id);
+    const analyticUnitId = ctx.request.query.id;
+    if(analyticUnitId === undefined) {
+      throw new Error('Cannot delete undefined id');
+    }
+    await AnalyticUnit.remove(analyticUnitId);
     ctx.response.body = {
       code: 200,
       message: 'Success'
     };
   } catch(e) {
+    console.error(e);
     ctx.response.status = 500;
     ctx.response.body = {
       code: 500,
-      message: `Deletion error: ${e.message}`
+      message: `DELETE /analyticUnits error: ${e.message}`
     };
   }
 }
diff --git a/server/src/routes/segments_router.ts b/server/src/routes/segments_router.ts
index da7e7ea..5739d46 100644
--- a/server/src/routes/segments_router.ts
+++ b/server/src/routes/segments_router.ts
@@ -1,32 +1,40 @@
 import * as AnalyticsController from '../controllers/analytics_controller';
 
-import { AnalyticUnitId, AnalyticUnitStatus } from '../models/analytic_unit_model';
+import { AnalyticUnitId } from '../models/analytic_unit_model';
 import * as Segment from '../models/segment_model';
 
 import * as Router from 'koa-router';
 
 
 async function getSegments(ctx: Router.IRouterContext) {
-  let id: AnalyticUnitId = ctx.request.query.id;
-  if(id === undefined || id === '') {
-    throw new Error('analyticUnitId (id) is missing');
-  }
-  let query: Segment.FindManyQuery = {};
-
-  if(!isNaN(+ctx.request.query.lastSegmentId)) {
-    query.intexGT = +ctx.request.query.lastSegmentId;
-  }
-  if(!isNaN(+ctx.request.query.from)) {
-    query.timeFromGTE = +ctx.request.query.from;
-  }
-  if(!isNaN(+ctx.request.query.to)) {
-    query.timeToLTE = +ctx.request.query.to;
-  }
+  try {
+    let id: AnalyticUnitId = ctx.request.query.id;
+    if(id === undefined || id === '') {
+      throw new Error('analyticUnitId (id) is missing');
+    }
+    let query: Segment.FindManyQuery = {};
 
-  let segments = await Segment.findMany(id, query);
+    if(!isNaN(+ctx.request.query.lastSegmentId)) {
+      query.intexGT = +ctx.request.query.lastSegmentId;
+    }
+    if(!isNaN(+ctx.request.query.from)) {
+      query.timeFromGTE = +ctx.request.query.from;
+    }
+    if(!isNaN(+ctx.request.query.to)) {
+      query.timeToLTE = +ctx.request.query.to;
+    }
 
-  ctx.response.body = { segments };
+    let segments = await Segment.findMany(id, query);
 
+    ctx.response.body = { segments };
+  } catch(e) {
+    console.error(e);
+    ctx.response.status = 500;
+    ctx.response.body = {
+      code: 500,
+      message: `GET /segments error: ${e.message}`
+    };
+  }
 }
 
 async function updateSegments(ctx: Router.IRouterContext) {
@@ -49,10 +57,11 @@ async function updateSegments(ctx: Router.IRouterContext) {
     ctx.response.body = { addedIds, removed };
     
   } catch(e) {
+    console.error(e);
     ctx.response.status = 500;
     ctx.response.body = {
       code: 500,
-      message: `Learning error: ${e.message}`
+      message: `PATCH /segments (learning) error: ${e.message}`
     };
   }
 }