diff --git a/guardrails_api/app.py b/guardrails_api/app.py
index 64e5180..27512f7 100644
--- a/guardrails_api/app.py
+++ b/guardrails_api/app.py
@@ -18,7 +18,6 @@
 import json
 import os
 
-
 # from pyinstrument import Profiler
 # from pyinstrument.renderers.html import HTMLRenderer
 # from pyinstrument.renderers.speedscope import SpeedscopeRenderer
diff --git a/guardrails_api/clients/pg_guard_client.py b/guardrails_api/clients/pg_guard_client.py
index c7a1f48..226232a 100644
--- a/guardrails_api/clients/pg_guard_client.py
+++ b/guardrails_api/clients/pg_guard_client.py
@@ -18,14 +18,20 @@ def __init__(self):
         self.initialized = True
         self.pgClient = PostgresClient()
 
+    def get_db(self):  # generator for local sessions
+        db = self.pgClient.SessionLocal()
+        try:
+            yield db
+        finally:
+            db.close()
+
     def get_guard(self, guard_name: str, as_of_date: str = None) -> GuardStruct:
-        latest_guard_item = (
-            self.pgClient.db.session.query(GuardItem).filter_by(name=guard_name).first()
-        )
+        db = next(self.get_db())
+        latest_guard_item = db.query(GuardItem).filter_by(name=guard_name).first()
         audit_item = None
         if as_of_date is not None:
             audit_item = (
-                self.pgClient.db.session.query(GuardItemAudit)
+                db.query(GuardItemAudit)
                 .filter_by(name=guard_name)
                 .filter(GuardItemAudit.replaced_on > as_of_date)
                 .order_by(GuardItemAudit.replaced_on.asc())
@@ -43,27 +49,29 @@ def get_guard(self, guard_name: str, as_of_date: str = None) -> GuardStruct:
         return from_guard_item(guard_item)
 
     def get_guard_item(self, guard_name: str) -> GuardItem:
-        return (
-            self.pgClient.db.session.query(GuardItem).filter_by(name=guard_name).first()
-        )
+        db = next(self.get_db())
+        return db.query(GuardItem).filter_by(name=guard_name).first()
 
     def get_guards(self) -> List[GuardStruct]:
-        guard_items = self.pgClient.db.session.query(GuardItem).all()
+        db = next(self.get_db())
+        guard_items = db.query(GuardItem).all()
 
         return [from_guard_item(gi) for gi in guard_items]
 
     def create_guard(self, guard: GuardStruct) -> GuardStruct:
+        db = next(self.get_db())
         guard_item = GuardItem(
             name=guard.name,
             railspec=guard.to_dict(),
             num_reasks=None,
             description=guard.description,
         )
-        self.pgClient.db.session.add(guard_item)
-        self.pgClient.db.session.commit()
+        db.add(guard_item)
+        db.commit()
         return from_guard_item(guard_item)
 
     def update_guard(self, guard_name: str, guard: GuardStruct) -> GuardStruct:
+        db = next(self.get_db())
         guard_item = self.get_guard_item(guard_name)
         if guard_item is None:
             raise HttpError(
@@ -76,21 +84,23 @@ def update_guard(self, guard_name: str, guard: GuardStruct) -> GuardStruct:
         # guard_item.num_reasks = guard.num_reasks
         guard_item.railspec = guard.to_dict()
         guard_item.description = guard.description
-        self.pgClient.db.session.commit()
+        db.commit()
         return from_guard_item(guard_item)
 
     def upsert_guard(self, guard_name: str, guard: GuardStruct) -> GuardStruct:
+        db = next(self.get_db())
         guard_item = self.get_guard_item(guard_name)
         if guard_item is not None:
             guard_item.railspec = guard.to_dict()
             guard_item.description = guard.description
             # guard_item.num_reasks = guard.num_reasks
-            self.pgClient.db.session.commit()
+            db.commit()
             return from_guard_item(guard_item)
         else:
             return self.create_guard(guard)
 
     def delete_guard(self, guard_name: str) -> GuardStruct:
+        db = next(self.get_db())
         guard_item = self.get_guard_item(guard_name)
         if guard_item is None:
             raise HttpError(
@@ -100,7 +110,7 @@ def delete_guard(self, guard_name: str) -> GuardStruct:
                     guard_name=guard_name
                 ),
             )
-        self.pgClient.db.session.delete(guard_item)
-        self.pgClient.db.session.commit()
+        db.delete(guard_item)
+        db.commit()
         guard = from_guard_item(guard_item)
         return guard
diff --git a/guardrails_api/clients/postgres_client.py b/guardrails_api/clients/postgres_client.py
index 951a4f4..56e1501 100644
--- a/guardrails_api/clients/postgres_client.py
+++ b/guardrails_api/clients/postgres_client.py
@@ -2,16 +2,24 @@
 import json
 import os
 import threading
-from flask import Flask
-from sqlalchemy import text
+from fastapi import FastAPI
 from typing import Tuple
-from guardrails_api.models.base import db, INIT_EXTENSIONS
+from sqlalchemy import create_engine, text
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+
+Base = declarative_base()
 
 
 def postgres_is_enabled() -> bool:
     return os.environ.get("PGHOST", None) is not None
 
 
+# Global variables for database session
+postgres_client = None
+SessionLocal = None
+
+
 class PostgresClient:
     _instance = None
     _lock = threading.Lock()
@@ -45,7 +53,17 @@ def get_pg_creds(self) -> Tuple[str, str]:
         pg_password = pg_password or os.environ.get("PGPASSWORD")
         return pg_user, pg_password
 
-    def initialize(self, app: Flask):
+    def get_db(self):
+        if postgres_is_enabled():
+            db = self.SessionLocal()
+            try:
+                yield db
+            finally:
+                db.close()
+        else:
+            yield None
+
+    def initialize(self, app: FastAPI):
         pg_user, pg_password = self.get_pg_creds()
         pg_host = os.environ.get("PGHOST", "localhost")
         pg_port = os.environ.get("PGPORT", "5432")
@@ -64,23 +82,64 @@ def initialize(self, app: Flask):
         if os.environ.get("NODE_ENV") == "production":
             conf = f"{conf}?sslmode=verify-ca&sslrootcert=global-bundle.pem"
 
-        app.config["SQLALCHEMY_DATABASE_URI"] = conf
+        engine = create_engine(conf)
+        SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
-        app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False
-        app.secret_key = "secret"
         self.app = app
-        self.db = db
-        db.init_app(app)
-        from guardrails_api.models.guard_item import GuardItem  # NOQA
-        from guardrails_api.models.guard_item_audit import (  # NOQA
-            GuardItemAudit,
-            AUDIT_FUNCTION,
-            AUDIT_TRIGGER,
-        )
+        self.engine = engine
+        self.SessionLocal = SessionLocal
+        # Create tables
+        from guardrails_api.models import GuardItem, GuardItemAudit  # noqa
+
+        Base.metadata.create_all(bind=engine)
+
+        # Execute custom SQL
+        with engine.connect() as connection:
+            connection.execute(text(INIT_EXTENSIONS))
+            connection.execute(text(AUDIT_FUNCTION))
+            connection.execute(text(AUDIT_TRIGGER))
+            connection.commit()
+
+
+# Define INIT_EXTENSIONS, AUDIT_FUNCTION, and AUDIT_TRIGGER here as they were in your original code
+INIT_EXTENSIONS = """
+-- Your SQL for initializing extensions
+DO $$
+BEGIN
+    IF NOT EXISTS (SELECT 1 FROM pg_extension WHERE extname = 'uuid-ossp') THEN
+        CREATE EXTENSION "uuid-ossp";
+    END IF;
+END $$;
+
+DO $$
+BEGIN
+    IF NOT EXISTS (SELECT 1 FROM pg_extension WHERE extname = 'vector') THEN
+        CREATE EXTENSION "vector";
+    END IF;
+END $$;
+"""
+
+AUDIT_FUNCTION = """
+CREATE OR REPLACE FUNCTION guard_audit_function() RETURNS TRIGGER AS $guard_audit$
+BEGIN
+    IF (TG_OP = 'DELETE') THEN
+    INSERT INTO guards_audit SELECT uuid_generate_v4(), OLD.*, now(), 'D';
+    ELSIF (TG_OP = 'UPDATE') THEN
+    INSERT INTO guards_audit SELECT uuid_generate_v4(), OLD.*, now(), 'U';
+    ELSIF (TG_OP = 'INSERT') THEN
+    INSERT INTO guards_audit SELECT uuid_generate_v4(), NEW.*, now(), 'I';
+    END IF;
+    RETURN null;
+END;
+$guard_audit$
+LANGUAGE plpgsql;
+"""
 
-        with self.app.app_context():
-            self.db.session.execute(text(INIT_EXTENSIONS))
-            self.db.create_all()
-            self.db.session.execute(text(AUDIT_FUNCTION))
-            self.db.session.execute(text(AUDIT_TRIGGER))
-            self.db.session.commit()
+AUDIT_TRIGGER = """
+DROP TRIGGER IF EXISTS guard_audit_trigger
+  ON guards;
+CREATE TRIGGER guard_audit_trigger
+    AFTER INSERT OR UPDATE OR DELETE ON guards
+    FOR EACH ROW
+    EXECUTE PROCEDURE guard_audit_function();
+"""
diff --git a/guardrails_api/models/__init__.py b/guardrails_api/models/__init__.py
index e69de29..391a299 100644
--- a/guardrails_api/models/__init__.py
+++ b/guardrails_api/models/__init__.py
@@ -0,0 +1,5 @@
+# __init__.py
+from .guard_item_audit import GuardItemAudit
+from .guard_item import GuardItem
+
+__all__ = ["GuardItemAudit", "GuardItem"]
diff --git a/guardrails_api/models/base.py b/guardrails_api/models/base.py
deleted file mode 100644
index 29f0169..0000000
--- a/guardrails_api/models/base.py
+++ /dev/null
@@ -1,8 +0,0 @@
-from flask_sqlalchemy import SQLAlchemy
-
-db = SQLAlchemy()
-
-INIT_EXTENSIONS = """
-CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
-CREATE EXTENSION IF NOT EXISTS "vector";
-"""
diff --git a/guardrails_api/models/guard_item.py b/guardrails_api/models/guard_item.py
index a2dbf32..6bcacfa 100644
--- a/guardrails_api/models/guard_item.py
+++ b/guardrails_api/models/guard_item.py
@@ -1,9 +1,9 @@
 from sqlalchemy import Column, String, Integer
 from sqlalchemy.dialects.postgresql import JSONB
-from guardrails_api.models.base import db
+from guardrails_api.clients.postgres_client import Base
 
 
-class GuardItem(db.Model):
+class GuardItem(Base):
     __tablename__ = "guards"
     # TODO: Make primary key a composite between guard.name and the guard owner's userId
     name = Column(String, primary_key=True)
diff --git a/guardrails_api/models/guard_item_audit.py b/guardrails_api/models/guard_item_audit.py
index 183626e..13ee3c2 100644
--- a/guardrails_api/models/guard_item_audit.py
+++ b/guardrails_api/models/guard_item_audit.py
@@ -1,9 +1,9 @@
 from sqlalchemy import Column, String, Integer
 from sqlalchemy.dialects.postgresql import JSONB, TIMESTAMP, CHAR
-from guardrails_api.models.base import db
+from guardrails_api.clients.postgres_client import Base
 
 
-class GuardItemAudit(db.Model):
+class GuardItemAudit(Base):
     __tablename__ = "guards_audit"
     id = Column(String, primary_key=True)
     name = Column(String, nullable=False, index=True)
@@ -35,29 +35,3 @@ def __init__(
         self.replaced_on = replaced_on
         self.operation = operation
         # self.owner = owner
-
-
-AUDIT_FUNCTION = """
-CREATE OR REPLACE FUNCTION guard_audit_function() RETURNS TRIGGER AS $guard_audit$
-BEGIN
-    IF (TG_OP = 'DELETE') THEN
-    INSERT INTO guards_audit SELECT uuid_generate_v4(), OLD.*, now(), 'D';
-    ELSIF (TG_OP = 'UPDATE') THEN
-    INSERT INTO guards_audit SELECT uuid_generate_v4(), OLD.*, now(), 'U';
-    ELSIF (TG_OP = 'INSERT') THEN
-    INSERT INTO guards_audit SELECT uuid_generate_v4(), NEW.*, now(), 'I';
-    END IF;
-    RETURN null;
-END;
-$guard_audit$
-LANGUAGE plpgsql;
-"""
-
-AUDIT_TRIGGER = """
-DROP TRIGGER IF EXISTS guard_audit_trigger
-  ON guards;
-CREATE TRIGGER guard_audit_trigger
-    AFTER INSERT OR UPDATE OR DELETE ON guards
-    FOR EACH ROW
-    EXECUTE PROCEDURE guard_audit_function();
-"""
diff --git a/guardrails_api/start-dev.sh b/guardrails_api/start-dev.sh
index 36f33ba..83a2d70 100755
--- a/guardrails_api/start-dev.sh
+++ b/guardrails_api/start-dev.sh
@@ -1,6 +1,6 @@
 gunicorn --bind 0.0.0.0:8000 \
          --timeout 120 \
-         --workers 3 \
+         --workers 2 \
          --threads 2 \
          --worker-class=uvicorn.workers.UvicornWorker \
          "guardrails_api.app:create_app()" \
diff --git a/pyproject.toml b/pyproject.toml
index d3d3d94..a2db2fb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -11,7 +11,6 @@ keywords = ["Guardrails", "Guardrails AI", "Guardrails API", "Guardrails API"]
 requires-python = ">= 3.8.1"
 dependencies = [
     "guardrails-ai>=0.5.6",
-    "Flask-SQLAlchemy>=3.1.1,<4",
     "Werkzeug>=3.0.3,<4",
     "jsonschema>=4.22.0,<5",
     "referencing>=0.35.1,<1",
@@ -27,6 +26,7 @@ dependencies = [
     "requests>=2.32.3",
     "aiocache>=0.11.1",
     "fastapi>=0.114.1",
+    "SQLAlchemy>=2.0.34",
 ]
 
 [tool.setuptools.dynamic]
@@ -42,6 +42,7 @@ dev = [
     "coverage",
     "pytest-mock",
     "gunicorn>=22.0.0,<23",
+    "uvicorn",
 ]
 
 [tool.pytest.ini_options]
diff --git a/requirements-lock.txt b/requirements-lock.txt
index 950b069..cacc27e 100644
--- a/requirements-lock.txt
+++ b/requirements-lock.txt
@@ -28,16 +28,10 @@ frozenlist==1.4.1
 fsspec==2024.6.1
 googleapis-common-protos==1.63.2
 griffe==0.36.9
-<<<<<<< Updated upstream
 grpcio==1.65.1
-guardrails-ai==0.5.7
+guardrails-ai==0.5.9
 guardrails-api-client==0.3.12
 guardrails_hub_types==0.0.4
-=======
-grpcio==1.64.1
-guardrails-ai==0.5.0a2
-guardrails-api-client==0.3.8
->>>>>>> Stashed changes
 gunicorn==22.0.0
 h11==0.14.0
 httpcore==1.0.5
diff --git a/tests/cli/test_start.py b/tests/cli/test_start.py
index e6973d9..befe21a 100644
--- a/tests/cli/test_start.py
+++ b/tests/cli/test_start.py
@@ -5,9 +5,9 @@
 def test_start(mocker):
     mocker.patch("guardrails_api.cli.start.cli")
 
-    mock_flask_app = MagicMock()
+    mock_app = MagicMock()
     mock_create_app = mocker.patch(
-        "guardrails_api.cli.start.create_app", return_value=mock_flask_app
+        "guardrails_api.cli.start.create_app", return_value=mock_app
     )
 
     from guardrails_api.cli.start import start