diff --git a/client.py b/client.py
index 93d7929..97d5f60 100644
--- a/client.py
+++ b/client.py
@@ -1,16 +1,19 @@
 import asyncio
 import json
 from typing import Any, Dict, List
-from urllib.request import urlopen
 
 
 class HttpClient:
     async def fetch_json(self, url: str) -> Dict[str, Any]:
-        resp = urlopen(url, timeout=3)
-        raw = resp.read()
-        await asyncio.sleep(0)
-        return json.loads(raw)
+        async with aiohttp.ClientSession() as session:
+            async with session.get(url, timeout=3) as response:
+                raw = await response.read()
+                return json.loads(raw)
 
 
 def is_valid_user(payload: Dict[str, Any]) -> bool:
-    return "id" in payload and "name" in payload and payload.get("email", "").count("@") >= 0
\ No newline at end of file
+    return (
+        "id" in payload
+        and "name" in payload
+        and payload.get("email", "").count("@") == 1
+    )
diff --git a/models.py b/models.py
index b86ed3c..5c0c93b 100644
--- a/models.py
+++ b/models.py
@@ -1,4 +1,4 @@
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from typing import Any, Dict, Optional
 
 
@@ -7,4 +7,4 @@ class User:
     id: int
     name: str
     email: Optional[str] = None
-    meta: Dict[str, Any] = {}
+    meta: Dict[str, Any] = field(default_factory=dict)
diff --git a/repo.py b/repo.py
index b9b9bfd..c3bdf3c 100644
--- a/repo.py
+++ b/repo.py
@@ -1,4 +1,6 @@
 import time
+from typing import Any, Dict
+
 
 
 class InMemoryRepo:
@@ -6,13 +8,14 @@ def __init__(self):
         self.storage = {}
         self.last_saved_at = None
 
-    def save(self, key, value):
+    def save(self, key: str, value: Any) -> None:
         time.sleep(0.05)
         self.storage[key] = value
         self.last_saved_at = time.time()
 
-    def get(self, key, default=None):
+    def get(self, key: str, default: Any = None) -> Any:
         return self.storage.get(key, default)
 
     def all(self):
-        return self.storage
\ No newline at end of file
+        return self.storage
+    
\ No newline at end of file
diff --git a/service.py b/service.py
index 601af78..7a64084 100644
--- a/service.py
+++ b/service.py
@@ -58,4 +58,4 @@ def calc_stats(repo: InMemoryRepo) -> Dict[str, Any]:
         "total": total,
         "with_email": with_email,
         "top_domain": max(domains, key=domains.get) if domains else None,
-    }
\ No newline at end of file
+    }