```python

from sqlalchemy import Column, Integer, String, Boolean
from app.db import Base

class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True, index=True)
    username = Column(String, unique=True, index=True)
    email = Column(String, unique=True, index=True)
    hashed_password = Column(String)
    is_active = Column(Boolean, default=True)
    is_superuser = Column(Boolean, default=False)

    def __repr__(self):
        return f"User(id={self.id}, username='{self.username}', email='{self.email}', is_active={self.is_active}, is_superuser={self.is_superuser})"
```


- `id`: An integer primary key and index.
- `username`: A string representing the user's username, which must be unique and indexed.
- `email`: A string representing the user's email address, which must be unique and indexed.
- `hashed_password`: A string representing the hashed password of the user.
- `is_active`: A boolean indicating whether the user is active or not, with a default value of `True`.
- `is_superuser`: A boolean indicating whether the user is a superuser or not, with a default value of `False`.

The `__repr__` method is defined to provide a string representation of the `User` object when printed.

Make sure to import the necessary modules and classes at the top of the file:

```python
from sqlalchemy import Column, Integer, String, Boolean
from app.db import Base
```

Here, `Column`, `Integer`, `String`, and `Boolean` are imported from the `sqlalchemy` module, and `Base` is imported from `app.db`, which is assumed to be the base class for SQLAlchemy models in your FastAPI application.

Note: This code assumes that you have already set up the necessary database connections and configurations for your FastAPI application using SQLAlchemy and SQLite.