What happens to transactions after they are processed? Where and how are they stored?

After a deal is processed, it is usually stored in a database for further analysis, reporting, and auditing. Depending on the system architecture, this could be a relational database management system (e.g., PostgreSQL, MySQL) or a NoSQL store (e.g., MongoDB, Cassandra).

The storage includes:

• Saving all key deal data (identifiers, amounts, statuses, timestamps).
• Logging status changes to track the deal's lifecycle.
• Possible archiving of old deals to optimize performance.

Example in Python using SQLAlchemy for saving a deal:

from sqlalchemy import create_engine, Column, Integer, String, Float
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class Deal(Base):
    __tablename__ = 'deals'
    id = Column(Integer, primary_key=True)
    status = Column(String)
    amount = Column(Float)

engine = create_engine('sqlite:///deals.db')
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()

# Create and save a deal
new_deal = Deal(status='processed', amount=1000.0)
session.add(new_deal)
session.commit()