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Module 4 · FastAPI for ML

Module 4: Machine Learning API Deployment Project

Deploy an insurance premium RandomForest model. Export Pipeline with joblib, serve requests via FastAPI endpoints, and connect Streamlit UI layers.

⏱ 28 Min Read Author: GenAIWallah Team Updated: May 2026
Day 7

Scikit-Learn Model Pipeline and Export

Why this matters

ML Pipeline: Sklearn pipelines bundle preprocessing + model — serialize once, load in the API process.

Train a sklearn Pipeline (preprocessing + estimator), evaluate offline, then serialize with joblib.dump.

  • Keep training notebooks separate from serving code
  • Version model artifacts (pipeline_v1.joblib)
  • Record feature order and dtypes expected at inference

Common mistakes

  • Blocking the event loop with heavy sync code in async routes.
  • Returning wrong HTTP status codes (200 on validation failure).
  • Shipping without request/response models for ML endpoints.

Interview checkpoints

  • Q: Explain ml pipeline in one minute. A: Definition + ML deployment angle.
  • Q: One FastAPI pitfall? A: Validation, async blocking, or wrong status code.

Practice

  1. Basic: Define ML Pipeline and give an example.
  2. Intermediate: Implement a minimal snippet for ML Pipeline.
  3. Advanced: Break it and read the OpenAPI / error response.

Recap

  • You can explain ml pipeline clearly.
  • You know one mistake to avoid.
  • You see how this connects to the next lesson.

Next: ML Serving

Day 8

FastAPI Serve Endpoint & Streamlit Frontend

Why this matters

ML Serving: Serving predictions via FastAPI + optional Streamlit UI is the standard ML demo-to-prod path.

Load the pipeline at startup; expose POST /predict with a Pydantic request body. Optional Streamlit front-end calls the API for demos.

import joblib
from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()
model = joblib.load("pipeline.joblib")

class Features(BaseModel):
    sepal_length: float
    sepal_width: float
    petal_length: float
    petal_width: float

@app.post("/predict")
def predict(x: Features):
    pred = model.predict([[x.sepal_length, x.sepal_width, x.petal_length, x.petal_width]])
    return {"class_id": int(pred[0])}
Production: For heavy models, use worker processes or run predict in a thread pool to avoid blocking async workers.

Common mistakes

  • Blocking the event loop with heavy sync code in async routes.
  • Returning wrong HTTP status codes (200 on validation failure).
  • Shipping without request/response models for ML endpoints.

Interview checkpoints

  • Q: Explain ml serving in one minute. A: Definition + ML deployment angle.
  • Q: One FastAPI pitfall? A: Validation, async blocking, or wrong status code.

Practice

  1. Basic: Define ML Serving and give an example.
  2. Intermediate: Implement a minimal snippet for ML Serving.
  3. Advanced: Break it and read the OpenAPI / error response.

Recap

  • You can explain ml serving clearly.
  • You know one mistake to avoid.
  • You see how this connects to the next lesson.

Next: Docker Intro

← Module 3: HTTP CRUD Module 5: Docker Containerization →