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Building Production ML Microservices: From Classical ML to RAG — A Template That Scales

How I built two production-grade ML systems using the same architectural pattern — and what I learned along the way.

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The Problem with Most ML Projects

Most ML tutorials end the same way — a Jupyter notebook, a trained model, maybe a Flask app if you're lucky. But none of them answer the real question:

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import numpy as np


class LinearRegression:

    def __init__(self, lr = 0.001, n_iters=1000):
        self.lr = lr
        self.n_iters = n_iters
        self.weights = None
        self.bias = None

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class Solution:
    def merge(self, nums1: List[int], m: int, nums2: List[int], n: int) -> None:
        """
        Do not return anything, modify nums1 in-place instead.
        """
        while(n>0):
            nums1[m+n-1]=nums2[n-1]
            n=n-1
        nums1.sort()

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Problem Statement

Brute Force Approach - In this approach, we'll consider each element and check for every next greater element

// Time Complexity - O(N^2)           Space Complexity - O(1)
class Solution {
public:
    vector<int> nextGreaterElements(vector<int>& nums) {
 vector result(nums.size(), -1); // Array to store next greater element of each element

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Problem Statement

Brute Force - We can use two extra vector in which one stores only zeroes and another stores non zeroes and then append zeroes from first array to another which contain non zeroes at beginning. But on leetcode, we have to solve it in-place.

Optimized Approach -

// Time Complexity - O(N)            Space Complexity - O(1)
class Solution {
public:

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Explain OAuth 2.0 .

OAuth 2.0, which stands for “Open Authorization”, is a standard designed to allow a website or application to access resources hosted by other web apps on behalf of a user. It replaced OAuth 1.0 in 2012 and is now the de facto industry standard for online authorization. OAuth 2.0 provides consented access and restricts actions of what the client app can perform on resources on behalf of the user, without ever sharing the user's credentials.

Principle - OAuth 2.0 is an authorization protocol and NOT an authentication protocol. As such, it is designed primarily as a means of granting access to a set of resources, for example, remote APIs or user data. OAuth 2.0 uses Access Tokens. An Access Token is a piece of data that represents the authorization to access resources on behalf of the end-user. OAuth 2.0 doesn’t define a specific format for Access Tokens. However, in some contexts, the JSON Web Token (JWT) format is often used. This enables token issuers to include data in the token

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Theory

Difference

Basis of Comparison	NoSQL	RDBMS
Definition	Non-relational databases, often known as distributed databases, are another name for NoSQL databases.	RDBMS, which stands for Relational Database Management Systems, is the most common name for SQL databases.
Query	No declarative query language	SQL stands for Structured Query Language.
Scalability	NoSQL databases are horizontally scalable	RDBMS databases are vertically scalable
Design	NoSQL combines multiple database technologies. These databases were created in response to the application's requirements.	Traditional RDBMS systems use SQL syntax and queries to get insights from data. Different OLAP systems use them.