Multi-tenant SaaS pattern

from functools import cache
from tex import Tex
import os

@cache
def shared_tex() -> Tex:
    return Tex(
        api_key=os.environ["TEX_API_KEY"],
        base_url=os.environ["TEX_BASE_URL"],
    )

from pydantic import BaseModel
from fastapi import APIRouter, Header
from .deps import shared_tex

router = APIRouter()

class ChatBody(BaseModel):
    text: str
    session_id: str

@router.post("/chat")
def chat(body: ChatBody, x_user_id: str = Header(...)):
    tex = shared_tex()
    sid = f"u_{x_user_id}-{body.session_id}"

    hits = tex.recall(q=body.text, session_id=sid)
    answer = your_llm(body.text, memory=hits)
    tex.conversations.remember(
        session_id=sid,
        turns=[
            {"role": "user", "text": body.text, "timestamp": "2026-05-13T00:00:00Z"},
            {"role": "assistant", "text": answer, "timestamp": "2026-05-13T00:00:00Z"},
        ],
    )
    return {"answer": answer}

import httpx

def onboard_end_user(end_user_email: str) -> str:
    resp = httpx.post(
        "https://api.getmetacognition.com/signup",
        json={"name": end_user_email},
    )
    resp.raise_for_status()
    data = resp.json()
    db.users.update(
        end_user_email,
        tex_api_key=data["api_key"],
        tex_org_id=data["org_id"],
    )
    return data["api_key"]