kaizakin

Act as my backend engineering interview mentor for top-tier software engineering internships. I am preparing for interviews where I need to demonstrate not just knowledge of backend technologies, but the ability to reason about systems, understand what happens underneath abstractions, identify bottlenecks, debug failures, and make engineering trade-offs. Every day, give me exactly ONE backend engineering interview problem.

Daily Rotation

Strictly rotate between these categories:

Day A — Core Engineering / Internals

Give me a deep conceptual problem involving one or more of:

Databases

• B-trees and indexes
• Database pages and storage layout

kaizakin

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    "javascript": "javascriptreact"
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  "editor.cursorSmoothCaretAnimation": "on",
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kaizakin

class Solution {
public:

    bool isvalid(vector<vector<char>>& board, int row, int col, char d){
        for(int i = 0; i<9; ++i){
            if(board[i][col] == d) return false;
            if(board[row][i] == d) return false;
        }

        int start_row = row/3 * 3;

kaizakin

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  "editor.defaultFormatter": "esbenp.prettier-vscode",
  "editor.formatOnSave": true,
  "editor.linkedEditing": true,
  "emmet.includeLanguages": {
    "javascript": "javascriptreact"
  },
  "editor.cursorSmoothCaretAnimation": "on",
  "editor.cursorBlinking": "smooth",

kaizakin

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    "editor.defaultFormatter": "esbenp.prettier-vscode",
    "editor.formatOnSave": true,
    "github.copilot.enable": {
        "*": false,
        "plaintext": false,
        "markdown": false,
        "scminput": false
    },

kaizakin

  "vim.useSystemClipboard": true,
  "vim.visualModeKeyBindingsNonRecursive": [
    {
      "before": ["p"],
      "commands": ["editor.action.clipboardPasteAction", "extension.vim_escape"]
    }
  ],
  "vim.easymotion": true,
  "vim.incsearch": true,
  "vim.useCtrlKeys": true,

kaizakin

int power(int x, int m) {
    int result = 1;
    while (m > 0) {
        if (m % 2 == 1) {
            result *= x;
        }
        x *= x;
        m /= 2;
    }
    return result;

kaizakin

import express from 'express';
import { S3Client, PutObjectCommand } from '@aws-sdk/client-s3';
import bodyParser from 'body-parser';
import dotenv from 'dotenv';
import fetch from 'node-fetch'; 

dotenv.config();

const app = express();
app.use(bodyParser.urlencoded({ extended: false }));