diff --git a/packages/cubejs-api-gateway/src/gateway.ts b/packages/cubejs-api-gateway/src/gateway.ts
index 82576a6986f1d..9c4adf181bdbf 100644
--- a/packages/cubejs-api-gateway/src/gateway.ts
+++ b/packages/cubejs-api-gateway/src/gateway.ts
@@ -1393,8 +1393,8 @@ class ApiGateway {
       });
 
       await res(queryType === QueryTypeEnum.REGULAR_QUERY ?
-        { sql: toQuery(sqlQueries[0]) } :
-        sqlQueries.map((sqlQuery) => ({ sql: toQuery(sqlQuery) })));
+        { sql: toQuery(sqlQueries[0]), dataSource: sqlQueries[0].dataSource } :
+        sqlQueries.map((sqlQuery) => ({ sql: toQuery(sqlQuery), dataSource: sqlQuery.dataSource })));
     } catch (e: any) {
       this.handleError({
         e, context, query, res, requestStarted
diff --git a/packages/cubejs-api-gateway/test/index.test.ts b/packages/cubejs-api-gateway/test/index.test.ts
index bf4a2b4d7fe9e..d5dbf9d6e2601 100644
--- a/packages/cubejs-api-gateway/test/index.test.ts
+++ b/packages/cubejs-api-gateway/test/index.test.ts
@@ -851,6 +851,43 @@ describe('API Gateway', () => {
     });
   });
 
+  describe('/v1/sql endpoint dataSource', () => {
+    test('returns dataSource for single query', async () => {
+      const { app } = await createApiGateway();
+      const query = JSON.stringify({ measures: ['Foo.bar'] });
+
+      const res = await request(app)
+        .get(`/cubejs-api/v1/sql?query=${encodeURIComponent(query)}`)
+        .set('Authorization', 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.e30.t-IDcSemACt8x4iTMCda8Yhe3iZaWbvV5XKSTbuAn0M')
+        .expect(200);
+
+      expect(res.body).toHaveProperty('sql');
+      expect(res.body).toHaveProperty('dataSource');
+      expect(res.body.dataSource).toBe('default');
+    });
+
+    test('returns dataSource for blending query', async () => {
+      const { app } = await createApiGateway();
+      const query = JSON.stringify([
+        { measures: ['Foo.bar'], timeDimensions: [{ dimension: 'Foo.time', granularity: 'day' }] },
+        { measures: ['Foo.bar'], timeDimensions: [{ dimension: 'Foo.time', granularity: 'day' }] }
+      ]);
+
+      const res = await request(app)
+        .get(`/cubejs-api/v1/sql?query=${encodeURIComponent(query)}`)
+        .set('Authorization', 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.e30.t-IDcSemACt8x4iTMCda8Yhe3iZaWbvV5XKSTbuAn0M')
+        .expect(200);
+
+      expect(Array.isArray(res.body)).toBe(true);
+      expect(res.body.length).toBe(2);
+      res.body.forEach((item: any) => {
+        expect(item).toHaveProperty('sql');
+        expect(item).toHaveProperty('dataSource');
+        expect(item.dataSource).toBe('default');
+      });
+    });
+  });
+
   describe('/cubejs-system/v1', () => {
     const scheduledRefreshContextsFactory = () => ([
       { securityContext: { foo: 'bar' } },
diff --git a/packages/cubejs-api-gateway/test/mocks.ts b/packages/cubejs-api-gateway/test/mocks.ts
index e9ffa95dbccd0..f2341b544c323 100644
--- a/packages/cubejs-api-gateway/test/mocks.ts
+++ b/packages/cubejs-api-gateway/test/mocks.ts
@@ -67,7 +67,8 @@ export const compilerApi = jest.fn().mockImplementation(async () => ({
         foo__bar: 'Foo.bar',
         foo__time: 'Foo.time',
       },
-      order: [{ id: 'id', desc: true, }]
+      order: [{ id: 'id', desc: true, }],
+      dataSource: 'default'
     };
   },
 
diff --git a/packages/cubejs-cubestore-driver/src/WebSocketConnection.ts b/packages/cubejs-cubestore-driver/src/WebSocketConnection.ts
index e3f6dfe800060..200017321dc83 100644
--- a/packages/cubejs-cubestore-driver/src/WebSocketConnection.ts
+++ b/packages/cubejs-cubestore-driver/src/WebSocketConnection.ts
@@ -14,16 +14,29 @@ import {
   HttpTable
 } from '../codegen';
 
+interface SentMessage {
+  resolve: (value: any) => void;
+  reject: (reason?: any) => void;
+  buffer: Uint8Array;
+}
+
+interface CubeStoreWebSocket extends WebSocket {
+  readyPromise: Promise<CubeStoreWebSocket>;
+  lastHeartBeat: Date;
+  sentMessages: Record<number, SentMessage>;
+  sendAsync: (message: Uint8Array) => Promise<void>;
+}
+
 export class WebSocketConnection {
   protected messageCounter: number;
 
-  protected maxConnectRetries: number;
+  protected readonly maxConnectRetries: number;
 
-  protected noHeartBeatTimeout: number;
+  protected readonly noHeartBeatTimeout: number;
 
   protected currentConnectionTry: number;
 
-  protected webSocket: any;
+  protected webSocket: CubeStoreWebSocket | null = null;
 
   private readonly url: string;
 
@@ -38,10 +51,10 @@ export class WebSocketConnection {
     this.connectionId = uuidv4();
   }
 
-  protected async initWebSocket() {
+  protected async initWebSocket(): Promise<CubeStoreWebSocket> {
     if (!this.webSocket) {
-      const webSocket: any = new WebSocket(this.url);
-      webSocket.readyPromise = new Promise<WebSocket>((resolve, reject) => {
+      const webSocket = new WebSocket(this.url) as CubeStoreWebSocket;
+      webSocket.readyPromise = new Promise<CubeStoreWebSocket>((resolve, reject) => {
         webSocket.lastHeartBeat = new Date();
         const pingInterval = setInterval(() => {
           if (webSocket.readyState === WebSocket.OPEN) {
@@ -53,12 +66,15 @@ export class WebSocketConnection {
           }
         }, 5000);
 
-        webSocket.sendAsync = async (message) => new Promise<void>((resolveSend, rejectSend) => {
+        webSocket.sendAsync = async (message: Uint8Array) => new Promise<void>((resolveSend, rejectSend) => {
           // If socket is closing this message should be resent
           if (webSocket.readyState === WebSocket.OPEN) {
             webSocket.send(message, (err) => {
               if (err) {
-                rejectSend(err);
+                rejectSend(new ConnectionError(
+                  `CubeStore connection error: ${err.message}`,
+                  err
+                ));
               } else {
                 resolveSend();
               }
@@ -81,7 +97,7 @@ export class WebSocketConnection {
           }
 
           if (webSocket === this.webSocket) {
-            this.webSocket = undefined;
+            this.webSocket = null;
           }
         });
         webSocket.on('pong', () => {
@@ -112,10 +128,10 @@ export class WebSocketConnection {
           }
 
           if (webSocket === this.webSocket) {
-            this.webSocket = undefined;
+            this.webSocket = null;
           }
         });
-        webSocket.on('message', async (msg) => {
+        webSocket.on('message', async (msg: Buffer) => {
           const buf = new flatbuffers.ByteBuffer(msg);
           const httpMessage = HttpMessage.getRootAsHttpMessage(buf);
           const resolvers = webSocket.sentMessages[httpMessage.messageId()];
@@ -179,10 +195,12 @@ export class WebSocketConnection {
           }
         });
       });
+
       webSocket.sentMessages = {};
       this.webSocket = webSocket;
     }
-    return this.webSocket.readyPromise;
+
+    return this.webSocket!.readyPromise;
   }
 
   private retryWaitTime() {
@@ -196,10 +214,14 @@ export class WebSocketConnection {
         socket.send(buffer, (err) => {
           if (err) {
             delete socket.sentMessages[messageId];
-            reject(err);
+            reject(new ConnectionError(
+              `CubeStore connection error: ${err.message}`,
+              err
+            ));
           }
         });
       }
+
       socket.sentMessages[messageId] = {
         resolve,
         reject,
diff --git a/packages/cubejs-cubestore-driver/src/errors.ts b/packages/cubejs-cubestore-driver/src/errors.ts
index cdef8bb88447d..df9f52529a375 100644
--- a/packages/cubejs-cubestore-driver/src/errors.ts
+++ b/packages/cubejs-cubestore-driver/src/errors.ts
@@ -7,6 +7,7 @@ export class ConnectionError extends CubeStoreError {
 
   public constructor(message: string, cause?: Error) {
     super(message);
+
     this.name = 'ConnectionError';
     this.cause = cause;
   }
@@ -15,6 +16,7 @@ export class ConnectionError extends CubeStoreError {
 export class QueryError extends CubeStoreError {
   public constructor(message: string) {
     super(message);
+
     this.name = 'QueryError';
   }
 }