diff --git a/backend/app/models.py b/backend/app/models.py
index 324ff9a..99a5478 100644
--- a/backend/app/models.py
+++ b/backend/app/models.py
@@ -1,82 +1,132 @@
 from sqlalchemy import Column, Integer, String, DateTime, Boolean, Text, ForeignKey, JSON
 from sqlalchemy.orm import relationship
-from datetime import datetime
+from datetime import datetime, timezone
 from .database import Base
 
+
 class Source(Base):
     __tablename__ = "sources"
-    
-    id = Column(Integer, primary_key=True, index=True)
+
+    id = Column(Integer, primary_key=True)
     name = Column(String, nullable=False)
     type = Column(String, nullable=False)  # local, ssh, database
-    config = Column(JSON, default=dict)
-    created_at = Column(DateTime, default=datetime.utcnow)
-    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
-    
+    config = Column(JSON, default=lambda: {})
+    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc))
+    updated_at = Column(
+        DateTime,
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+    )
+
     jobs = relationship("Job", back_populates="source", cascade="all, delete-orphan")
 
+    def __repr__(self):
+        return f"<Source(id={self.id}, name='{self.name}', type='{self.type}')>"
+
+
 class Job(Base):
     __tablename__ = "jobs"
-    
-    id = Column(Integer, primary_key=True, index=True)
+
+    id = Column(Integer, primary_key=True)
     name = Column(String, nullable=False)
-    source_id = Column(Integer, ForeignKey("sources.id"), nullable=False)
+    source_id = Column(Integer, ForeignKey("sources.id"), nullable=False, index=True)
     strategy = Column(String, nullable=False, default="full")  # full, incremental
     destination_path = Column(String, nullable=False)
-    exclude_patterns = Column(JSON, default=list)
+    exclude_patterns = Column(JSON, default=lambda: [])
     enabled = Column(Boolean, default=True)
-    created_at = Column(DateTime, default=datetime.utcnow)
-    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
-    
+    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc))
+    updated_at = Column(
+        DateTime,
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+    )
+
     source = relationship("Source", back_populates="jobs")
-    schedule = relationship("Schedule", back_populates="job", uselist=False, cascade="all, delete-orphan")
-    executions = relationship("JobExecution", back_populates="job", cascade="all, delete-orphan")
+    schedule = relationship(
+        "Schedule", back_populates="job", uselist=False, cascade="all, delete-orphan"
+    )
+    executions = relationship(
+        "JobExecution", back_populates="job", cascade="all, delete-orphan"
+    )
+
+    def __repr__(self):
+        return f"<Job(id={self.id}, name='{self.name}', source_id={self.source_id})>"
+
 
 class Schedule(Base):
     __tablename__ = "schedules"
-    
-    id = Column(Integer, primary_key=True, index=True)
-    job_id = Column(Integer, ForeignKey("jobs.id"), unique=True, nullable=False)
+
+    id = Column(Integer, primary_key=True)
+    job_id = Column(
+        Integer, ForeignKey("jobs.id"), unique=True, nullable=False, index=True
+    )
     cron_expression = Column(String, nullable=False)
     enabled = Column(Boolean, default=True)
-    created_at = Column(DateTime, default=datetime.utcnow)
-    
+    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc))
+
     job = relationship("Job", back_populates="schedule")
 
+    def __repr__(self):
+        return f"<Schedule(id={self.id}, job_id={self.job_id}, cron='{self.cron_expression}')>"
+
+
 class JobExecution(Base):
     __tablename__ = "job_executions"
-    
-    id = Column(Integer, primary_key=True, index=True)
-    job_id = Column(Integer, ForeignKey("jobs.id"), nullable=False)
-    status = Column(String, nullable=False, default="pending")  # pending, running, success, failed, cancelled
+
+    id = Column(Integer, primary_key=True)
+    job_id = Column(Integer, ForeignKey("jobs.id"), nullable=False, index=True)
+    status = Column(
+        String, nullable=False, default="pending"
+    )  # pending, running, success, failed, cancelled
     started_at = Column(DateTime, nullable=True)
     completed_at = Column(DateTime, nullable=True)
     bytes_processed = Column(Integer, default=0)
     bytes_backed_up = Column(Integer, default=0)
     error_message = Column(Text, nullable=True)
     triggered_by = Column(String, nullable=False)  # manual, schedule
-    
+
     job = relationship("Job", back_populates="executions")
-    backups = relationship("Backup", back_populates="execution", cascade="all, delete-orphan")
+    backups = relationship(
+        "Backup", back_populates="execution", cascade="all, delete-orphan"
+    )
+
+    def __repr__(self):
+        return f"<JobExecution(id={self.id}, job_id={self.job_id}, status='{self.status}')>"
+
 
 class Backup(Base):
     __tablename__ = "backups"
-    
-    id = Column(Integer, primary_key=True, index=True)
-    execution_id = Column(Integer, ForeignKey("job_executions.id"), nullable=False)
+
+    id = Column(Integer, primary_key=True)
+    execution_id = Column(
+        Integer, ForeignKey("job_executions.id"), nullable=False, index=True
+    )
     storage_path = Column(String, nullable=False)
     size_bytes = Column(Integer, default=0)
     checksum = Column(String, nullable=True)
     type = Column(String, nullable=False)  # full, incremental
-    parent_backup_id = Column(Integer, ForeignKey("backups.id"), nullable=True)
-    created_at = Column(DateTime, default=datetime.utcnow)
-    
+    parent_backup_id = Column(
+        Integer, ForeignKey("backups.id"), nullable=True, index=True
+    )
+    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc))
+
     execution = relationship("JobExecution", back_populates="backups")
     parent_backup = relationship("Backup", remote_side=[id])
 
+    def __repr__(self):
+        return f"<Backup(id={self.id}, execution_id={self.execution_id}, type='{self.type}')>"
+
+
 class Setting(Base):
     __tablename__ = "settings"
-    
+
     key = Column(String, primary_key=True)
     value = Column(Text, nullable=True)
-    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+    updated_at = Column(
+        DateTime,
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+    )
+
+    def __repr__(self):
+        return f"<Setting(key='{self.key}', value='{self.value}')>"