Forem: Brajesh Lovanshi

New to a Large Project? This Is How I Decode Complex Databases

Brajesh Lovanshi — Wed, 17 Dec 2025 17:08:47 +0000

When you join a large-scale project:

Multiple microservices
Each service has its own database
Each database has dozens of tables
Each table has millions of rows

As a new developer or QA, the biggest struggle is:

"Where is the data coming from and how are things connected?"

Asking others every time slows you down and reduces confidence. So here is a step-by-step approach I use to understand the database on my own.

Step 1: Start From the Business Flow (Not Tables)

Ask yourself what is the core business flow? (order, payment, user, inventory, etc.)
Example:

Order Service → order, order_items
Payment Service → payments, transactions
User Service → users, addresses

👉 This prevents random table jumping.

Step 2: Identify the "Anchor Table"

In every service, there is one main table.
Examples:

orders
users
payments

This table usually:

Has id, status, created_at

DESC orders; SELECT * FROM orders LIMIT 10;

Step 3: Use Naming Conventions to Detect Relationships

In microservice-based Database:

Foreign keys are often not enforced
Relationships are logical, not physical

Look for:

order_id
user_id
payment_id

Example:

SELECT * FROM order_items WHERE order_id = ?;

👉 Column names tell the story even without FK constraints.

Step 4: Track Data Using Real IDs (Reverse Engineering)

Pick one real record and follow it everywhere.
Example flow:

Get one order_id
Search it in:
payments
order_items
shipment
audit tables

SELECT * FROM payments WHERE order_id = 123;

👉 This builds mental mapping very fast.

Step 5: Understand Status Columns Deeply

Status columns are more important than relationships.

SELECT DISTINCT status FROM orders;

👉 This explains 80% of production bugs.

Step 6: Read Application Code Just for Repositories/DAOs

You don't need full code understanding.
Just search for: Repository, SQL queries, JPA entities

Step 7: Draw Your Own Simple Diagram Or Maintain Notes

No fancy tools needed.
Just draw:
Table names
Arrows using *_id
Status flow

Also maintain a notes, create a small doc:
Table name, Purpose, Important columns

Even a rough diagram and notes gives huge clarity.

Large MySQL databases in microservice systems look scary at first.
But they are just well-organized business flows stored in tables.
Hope this will help you nd add some value in your life, follow for more😊

🔥 Kadane's Algorithm — The Power of Maximum Subarrays

Brajesh Lovanshi — Thu, 17 Apr 2025 13:04:18 +0000

*Used in Amazon, Google, Microsoft Interviews 🚀
*

Hey devs 👋
If you’ve ever struggled with finding the maximum sum of a subarray, this is the trick you were probably missing: Kadane’s Algorithm.

It’s not just smart.
It’s ✨ interview magic ✨ — used by FAANG companies and loved by competitive programmers.

**📌 What is Kadane's Algorithm?
**Kadane’s Algorithm is a dynamic programming approach used to find the maximum sum of a contiguous subarray in linear time.

_Example problem:
_
Given an array [-2,1,-3,4,-1,2,1,-5,4],
Find the subarray with the maximum sum.
Answer: [4, -1, 2, 1] with sum = 6

**⚙️ How does Kadane's Algorithm work?
**Kadane’s magic is this:
👉 At every index, decide:

Should I start a new subarray here?
Or continue the previous one?
You track two values:

currentSum: Max sum ending at the current index
maxSum: Global max across the array

int maxSum = nums[0];
int currentSum = nums[0];

for (int i = 1; i < nums.length; i++) {
    currentSum = Math.max(nums[i], currentSum + nums[i]);
    maxSum = Math.max(maxSum, currentSum);
}

Time Complexity: O(n)
Space Complexity: O(1)

💡 When to Use Kadane's?
When you need to find maximum/minimum sum of contiguous elements
When the array has positive and negative numbers
In profit gain, sensor data analysis, pattern detection

If you like please subscribe for such more concept and follow me on linkedIn for quick learning:

🌀 Cycle Sort: Asked in Amazon, Google, and Microsoft

Brajesh Lovanshi — Thu, 10 Apr 2025 05:58:39 +0000

Hello folks 👋,

Recently, I came across Cycle Sort, and it instantly caught my attention due to its simplicity and power, especially in solving some tricky array problems. It's also been asked in interviews at Amazon, Google, and Microsoft — so it's definitely worth knowing!

In this post, I'll explain Cycle Sort, when to use it, and show you some popular problems that can be solved using it.

📘 What is Cycle Sort?
Cycle Sort is a sorting algorithm that works by placing each element at its correct index in the minimum number of writes.
It's mainly useful when you’re dealing with arrays where:

All numbers are in a range (like 0 to N or 1 to N)
The array may contain missing or duplicate values
It is an in-place sorting algorithm with O(n) time complexity in the best case and also uses O(1) space.

⏰ When to Use Cycle Sort?
Use Cycle Sort when:

You're given an array with elements from 1 to N or 0 to N
You're solving problems related to:
Missing numbers
Duplicate numbers
Correct positioning based on value
It’s not a general-purpose sorting algorithm, but it’s perfect for certain types of interview problems.

✅ Problems Solved Using Cycle Sort
Here are some important problems you can easily solve using Cycle Sort technique:

please find the problems with solutions on my GitHub :
https://github.com/br-lovanshi/Python_basic_to_advance

Solved Problems:
- ✅ Missing Number (LeetCode)
- ✅ Find All Numbers Disappeared in an Array
- ✅ Find the Duplicate Number
- ✅ First Missing Positive
- ✅ Set Mismatch

public class CycleSort {

    public static void cycleSort(int[] arr) {
        int i = 0;
        while (i < arr.length) {
            int correctIndex = arr[i] - 1;
            if (arr[i] != arr[correctIndex]) {
                // swap arr[i] with arr[correctIndex]
                int temp = arr[i];
                arr[i] = arr[correctIndex];
                arr[correctIndex] = temp;
            } else {
                i++;
            }
        }
    }

    public static void main(String[] args) {
        int[] nums = {3, 5, 2, 1, 4};
        cycleSort(nums);
        System.out.print("Sorted array: ");
        for (int num : nums) {
            System.out.print(num + " ");
        }
    }
}

I’ve solved all of these using Cycle Sort, and the logic becomes very clean and easy once you understand the concept.

Cycle Sort is one of those hidden gems in DSA — not commonly used in real-world sorting tasks, but incredibly powerful for specific interview questions.

If you're preparing for top tech interviews, I highly recommend learning it and practicing the problems above!

Let me know what you think — and feel free to share more problems where this helped you!

Happy coding! 🚀