@@ -44,6 +44,8 @@ jobs:
             path: Chapter04/quote-service
           - name: api-gateway
             path: Chapter05/api-gateway
+          - name: registration-service
+            path: Chapter06/registration-service
           - name: sitters-catalog
             path: Chapter07/sitters-catalog
           - name: authenticator-service
 
@@ -0,0 +1,2 @@
+*.db
+*.db-*
@@ -0,0 +1,38 @@
+# Chapter 6: Registration Service
+
+This is the final version of the chapter's SQLAlchemy service, including the three exercises. It uses Python 3.13 and uv. Run these commands from this directory:
+
+```bash
+uv sync
+uv run alembic upgrade head
+uv run fastapi dev main.py
+```
+
+Open http://127.0.0.1:8000/docs to register, list, read, update, and delete users. This is a teaching example with no authentication or authorization; do not expose it publicly. Access controls are covered later in the book.
+
+## Database setup
+
+SQLite is the default and needs no server. The final application does not create tables at startup: run the committed migrations before starting it against an empty database. Do not generate a second initial migration. If following the earlier `create_all` example, use a fresh database for the migration walkthrough rather than applying the initial migration to an existing `users` table.
+
+For PostgreSQL, provision a database and supply a `postgresql+asyncpg` connection URL through `DATABASE_URL` using your deployment's secret management. Never commit real credentials. Run the same migrations and `uv run python check_db.py` before starting the service. The check script also supports SQLite.
+
+The migrations create the seven-column users table, add the optional phone number, and add JSON preferences. Preferences use JSONB on PostgreSQL and JSON on SQLite. Python-side defaults are applied by SQLAlchemy, not by direct database inserts.
+
+## Tests
+
+```bash
+uv run pytest -v
+uv run ruff check .
+```
+
+Tests use temporary SQLite databases and do not connect to the configured application database. They cover the chapter's eight API cases, stored password hashing, validation, pagination, concurrent-duplicate handling, and migration upgrades/downgrades that preserve existing users. PostgreSQL integration must be checked separately against a running server.
+
+Compared with the printed snippets, the runnable service also returns 409 if a duplicate insert wins a race and rejects explicit null updates to non-nullable columns. Omitted update fields remain unchanged.
+
+## Exercises
+
+- **6.1:** `crud.get_users` and `GET /users` provide pagination ordered by user ID, with validated bounds.
+- **6.2:** `User.phone_number`, `UserBase.phone_number`, and migration `0002` add an optional phone number without deleting users.
+- **6.3:** `exercises/slot_repository.py` implements Chapter 3's `AvailabilitySlotRepository`. It imports the existing domain rather than duplicating it; pytest adds the Chapter 3 service to its Python path. The tests also run the unchanged Chapter 3 use cases against this adapter.
+
+The slot repository is synchronous because Chapter 3's repository interface is synchronous. Its separate metadata is not part of the registration database migrations. Construct it with a SQLAlchemy `sessionmaker` and inject it in place of the in-memory repository. The example does not implement concurrent reservation conflict detection.
@@ -0,0 +1,4 @@
+[alembic]
+script_location = %(here)s/alembic
+prepend_sys_path = %(here)s
+path_separator = os
@@ -0,0 +1,52 @@
+import asyncio
+
+from sqlalchemy import pool
+from sqlalchemy.ext.asyncio import async_engine_from_config
+
+from alembic import context
+from database import DATABASE_URL
+from models import Base
+
+config = context.config
+config.set_main_option(
+    "sqlalchemy.url", DATABASE_URL.replace("%", "%%")
+)
+target_metadata = Base.metadata
+
+
+def run_migrations_offline() -> None:
+    context.configure(
+        url=DATABASE_URL,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection) -> None:
+    context.configure(
+        connection=connection, target_metadata=target_metadata
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations() -> None:
+    connectable = async_engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+    try:
+        async with connectable.connect() as connection:
+            await connection.run_sync(do_run_migrations)
+    finally:
+        await connectable.dispose()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    asyncio.run(run_async_migrations())
@@ -0,0 +1,21 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}
@@ -0,0 +1,37 @@
+"""Create the seven-column users table."""
+
+import sqlalchemy as sa
+
+from alembic import op
+
+revision = "0001"
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "users",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column("email", sa.String(255), nullable=False),
+        sa.Column("full_name", sa.String(255), nullable=False),
+        sa.Column(
+            "hashed_password", sa.String(255), nullable=False
+        ),
+        sa.Column("role", sa.String(50), nullable=False),
+        sa.Column("is_active", sa.Boolean(), nullable=False),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            nullable=False,
+        ),
+    )
+    op.create_index(
+        "ix_users_email", "users", ["email"], unique=True
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("ix_users_email", table_name="users")
+    op.drop_table("users")
@@ -0,0 +1,22 @@
+"""Exercise 6.2: add an optional phone number."""
+
+import sqlalchemy as sa
+
+from alembic import op
+
+revision = "0002"
+down_revision = "0001"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "users",
+        sa.Column("phone_number", sa.String(50), nullable=True),
+    )
+
+
+def downgrade() -> None:
+    with op.batch_alter_table("users") as batch_op:
+        batch_op.drop_column("phone_number")
@@ -0,0 +1,27 @@
+"""Add portable JSON preferences."""
+
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import JSONB
+
+from alembic import op
+
+revision = "0003"
+down_revision = "0002"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "users",
+        sa.Column(
+            "preferences",
+            sa.JSON().with_variant(JSONB, "postgresql"),
+            nullable=True,
+        ),
+    )
+
+
+def downgrade() -> None:
+    with op.batch_alter_table("users") as batch_op:
+        batch_op.drop_column("preferences")
@@ -0,0 +1,25 @@
+import asyncio
+
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import create_async_engine
+
+from database import DATABASE_URL
+
+
+async def main() -> None:
+    engine = create_async_engine(DATABASE_URL)
+    query = (
+        "SELECT sqlite_version()"
+        if engine.dialect.name == "sqlite"
+        else "SELECT version()"
+    )
+    try:
+        async with engine.connect() as conn:
+            version = await conn.scalar(text(query))
+        print(f"Connected to: {version}")
+    finally:
+        await engine.dispose()
+
+
+if __name__ == "__main__":
+    asyncio.run(main())