diff --git a/argos/server/models.py b/argos/server/models.py
index 451eb6b..0637e7e 100644
--- a/argos/server/models.py
+++ b/argos/server/models.py
@@ -93,7 +93,8 @@ class Result(Base):
     __tablename__ = "results"
     id: Mapped[int] = mapped_column(primary_key=True)
     task_id: Mapped[int] = mapped_column(ForeignKey("tasks.id"))
-    task: Mapped["Task"] = relationship(back_populates="results")
+    task: Mapped["Task"] = relationship(back_populates="results",
+                                        cascade="save-update, merge, delete")
     agent_id: Mapped[str] = mapped_column(nullable=True)
 
     submitted_at: Mapped[datetime] = mapped_column()
@@ -112,3 +113,13 @@ class Result(Base):
 
     def __str__(self):
         return f"DB Result {self.id} - {self.status} - {self.context}"
+
+class ConfigCache(Base):
+    """Contains some informations on the previous config state
+
+    Used to quickly determine if we need to update the tasks
+    """
+    __tablename__ = "config_cache"
+    name: Mapped[str] = mapped_column(primary_key=True)
+    val: Mapped[str] = mapped_column()
+    updated_at: Mapped[datetime] = mapped_column()
diff --git a/argos/server/queries.py b/argos/server/queries.py
index 271b2c9..345f480 100644
--- a/argos/server/queries.py
+++ b/argos/server/queries.py
@@ -1,5 +1,7 @@
 """Functions to ease SQL queries management"""
 from datetime import datetime, timedelta
+from hashlib import sha256
+from typing import List
 from urllib.parse import urljoin
 
 from sqlalchemy import desc, func
@@ -7,7 +9,7 @@ from sqlalchemy.orm import Session
 
 from argos import schemas
 from argos.logging import logger
-from argos.server.models import Result, Task
+from argos.server.models import Result, Task, ConfigCache
 
 
 async def list_tasks(db: Session, agent_id: str, limit: int = 100):
@@ -60,10 +62,64 @@ async def count_results(db: Session):
     return db.query(Result).count()
 
 
+async def is_config_unchanged(db: Session, config: schemas.Config) -> bool:
+    """Check if websites config has changed by using a hashsum and a config cache"""
+    websites_hash = sha256(str(config.websites).encode()).hexdigest()
+    conf_caches = (
+        db.query(ConfigCache)
+        .all()
+    )
+    same_config = True
+    if conf_caches:
+        for conf in conf_caches:
+            if not same_config:
+                break
+
+            if conf.name == 'websites_hash':
+                same_config = conf.val == websites_hash
+            elif conf.name == 'general_frequency':
+                same_config = conf.val == str(config.general.frequency)
+
+        if same_config:
+            return True
+
+        for conf in conf_caches:
+            if conf.name == 'websites_hash':
+                conf.val = websites_hash
+            elif conf.name == 'general_frequency':
+                conf.val = config.general.frequency
+            conf.updated_at = datetime.now()
+    else:
+        web_hash = ConfigCache(
+                name='websites_hash',
+                val=websites_hash,
+                updated_at=datetime.now()
+        )
+        gen_freq = ConfigCache(
+                name='general_frequency',
+                val=str(config.general.frequency),
+                updated_at=datetime.now()
+        )
+        db.add(web_hash)
+        db.add(gen_freq)
+        db.commit()
+
+    return False
+
+
 async def update_from_config(db: Session, config: schemas.Config):
     """Update tasks from config file"""
+    config_unchanged = await is_config_unchanged(db, config)
+    if config_unchanged:
+        return None
+
+    max_task_id = (
+        db.query(func.max(Task.id).label('max_id')) #  pylint: disable-msg=not-callable
+        .all()
+    )[0].max_id
     tasks = []
     unique_properties = []
+    seen_tasks: List[int] = []
     for website in config.websites:
         domain = str(website.domain)
         frequency = website.frequency or config.general.frequency
@@ -83,6 +139,7 @@ async def update_from_config(db: Session, config: schemas.Config):
                 )
                 if existing_tasks:
                     existing_task = existing_tasks[0]
+                    seen_tasks.append(existing_task.id)
 
                     if frequency != existing_task.frequency:
                         existing_task.frequency = frequency
@@ -107,6 +164,18 @@ async def update_from_config(db: Session, config: schemas.Config):
     db.add_all(tasks)
     db.commit()
 
+    # Delete vanished tasks
+    if max_task_id:
+        vanished_tasks = (
+            db.query(Task)
+            .filter(
+                Task.id <= max_task_id,
+                Task.id.not_in(seen_tasks)
+            ).delete()
+        )
+        db.commit()
+        logger.info("%i tasks has been removed since not in config file anymore", vanished_tasks)
+
 
 async def get_severity_counts(db: Session) -> dict:
     """Get the severities (ok, warning, critical…) and their count"""
diff --git a/tests/test_queries.py b/tests/test_queries.py
index 8770d98..d92c750 100644
--- a/tests/test_queries.py
+++ b/tests/test_queries.py
@@ -78,7 +78,7 @@ async def test_update_from_config_with_duplicate_tasks(db, empty_config):
 
 
 @pytest.mark.asyncio
-async def test_update_from_config_db_can_handle_already_present_duplicates(
+async def test_update_from_config_db_can_remove_duplicates_and_old_tasks(
     db, empty_config, task
 ):
     # Add a duplicate in the db
@@ -99,12 +99,28 @@ async def test_update_from_config_db_can_handle_already_present_duplicates(
             dict(
                 path="https://another-example.com", checks=[{task.check: task.expected}]
             ),
+            dict(
+                path=task.url, checks=[{task.check: task.expected}]
+            ),
         ],
     )
     empty_config.websites = [website]
 
     await queries.update_from_config(db, empty_config)
-    assert db.query(Task).count() == 3
+    assert db.query(Task).count() == 2
+
+    website = schemas.config.Website(
+        domain=task.domain,
+        paths=[
+            dict(
+                path="https://another-example.com", checks=[{task.check: task.expected}]
+            ),
+        ],
+    )
+    empty_config.websites = [website]
+
+    await queries.update_from_config(db, empty_config)
+    assert db.query(Task).count() == 1
 
 
 @pytest.mark.asyncio