BCG Interview Questions, Process, and Tips

Q1. Introduce yourself.
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Q2. Walk me through your work experience.
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Q3. Couple of questions related to GST policy as they were relevant to work experience.
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Our client is a large infrastructure player, who wants to build a 10km-long tollway bridge connecting 2 cities divided by a river. Please advise them on its profitability.
[Please note that I stands for Interviewer and C stands for Candidate] 

I: The cities are currently connected by a 30km-long 4-lane bridge (no toll). Our client wants to shorten this distance to 10 km with a new 8-lane bridge, with a profitability objective.

Major use cases of the bridge users: work, education, personal/leisure activities.

C: Noted. My approach to this problem would be first doing a qualitative check for size of opportunity & risks, followed by a quantitative approach where we can calculate the NPV to check if it is positive.

I: Works. Let’s start with the Qualitative part.

C: Great. Here, I want to break it down into 2 parts: opportunity & risk. By opportunity, I want to look at what will be the traffic between the cities across the 2 bridges and its spread across each bridge. And in risk, I will have a look at major sources of risks such as Political risk, Regulatory risk and Relocation & rehabilitation risks.

I: Great. You already know the reasons why people travel between the 2 cities. What are your thoughts on the Opportunity bit?

C: Given that the distance between the 2 cities has reduced by 20 km (30-10), I would imagine a lot more people would be interested in travelling between the cities now, despite the additional toll to be paid.

I: Definitely. Let’s assume that qualitatively the risks don’t seem major as well. Let’s move onto the quantitative part of it.

C: Alright. Here, I want to estimate the NPV of the project and if positive, compare that with the infra company’s existing profits: if it is significant in comparison, only then will we go ahead with the project.

I: Perfect. Let’s begin.

C: I want to first look at the major revenue segments: toll, proceeds from rent & sale of real estate assets on the bridge, advertisements, tourism opportunities and parking. Fair to assume to these heads would encapsulate most of the revenue earned, am I missing something?

I: No. How will you estimate the revenue earned from toll, say in a day?

C: To estimate the revenue earned from toll in a day, I would first guesstimate the number of vehicles travelling between the 2 cities in a day and estimate what will be our bridge’s share of the traffic. After that, I would estimate a fair price of a toll ticket.

I: Great. Please lay down your approaches for each estimate.

C: Number of vehicles guesstimate: Used the Supply side: divided a day into Low/Medium/High traffic hours. Low traffic: one vehicle passes the tollgate every 20 seconds, medium: 10 seconds, high: 4 seconds. From the number of hours in each L/M/H traffic segments, will guesstimate the number of vehicles in each lane.

Multiply by 8 lanes. Toll Pricing: Used value-based pricing (alternate: cost-based, but the interviewer asked for value-based); By using our bridge as opposed to the existing bridge, each commuter saves time and petrol (thanks to lesser distance).

Petrol saved = 20 km worth of petrol, if the average vehicle’s mileage is 20 km, then we save 1 liter of petrol each way (~Rs. 70).

To calculate the monetary value of time saved (45 mins. (10 km at 40 kmph vs 30 km at 30 kmph average): we can multiply 45 minutes with the hourly salary of the commuter of the bridge with the minimum earnings/car owner. This way we can ensure affordability for all.

Final toll price (one way) = value added due to time saved + value-added due to petrol saved (Rs. 70). This can then be further discounted for monthly pass or return passes.

I: Great. Your thoughts on using the demand side approach for calculating traffic volume?

C: We can do that by estimating how many people would want to travel to the other city for each use case, despite the distance. For example, we need to estimate the number of school students for which the following equation is true ->[Value (Schooling in same city) < {Value (Schooling in other city): Cost (Monetary & Hedonic) of travelling to the other city}]

However, this is a difficult estimate with a lot of room for error. Hence, I would prefer the supply side calculation.

I: Great. Your thoughts on the cost side of NPV?

C: There will be a large capital expenditure, followed by periodic maintenance expenses.

I: Okay. How will you estimate the NPV from these?

C: Subtract costs from the revenue estimates over time, & discount it by the COC of the project.

I: Okay. Thoughts on the cost of capital of such projects?

C: Mostly high. These projects are mostly financed via non-recourse loans, with lenders having first claim to the cash flows emanating from the project till such time the project is paid for. Since this is a risky proposition for the lender, the cost of capital is usually high.

I: Great. Let’s do some calculations for the NPV and wind up.

Q1. Basics of Python, Flask, ReactJs, RestApi Development
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Q2. Python - Difference between is and ==
Ans. 
The 'is' operator checks if two variables point to the same object in memory, while '==' checks if the values of the two variables are equal.
• Use 'is' to check if two variables reference the same object in memory

• Use '==' to check if the values of two variables are equal

• Example: a = [1, 2, 3]; b = a; a is b will return True, a == b will also return True
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Q3. React - useEffect vs useState
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useEffect is used for side effects in functional components, while useState is used for managing state.
• useEffect is used to perform side effects in functional components, like data fetching, subscriptions, or manually changing the DOM

• useState is used to manage state in functional components, allowing the component to re-render when the state changes

• Example: useEffect can be used to fetch data from an API when the compo...read more
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Q4. Authentication in RestApi
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Authentication in RestApi involves verifying the identity of users before granting access to resources.
• Use tokens (JWT) for authentication

• Implement OAuth for secure authentication

• Utilize session management for user authentication

• Implement two-factor authentication for added security
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Q5. React - Pure Component and Higher order components
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Asked coding questions on Python and SQL
Python - find longest non repeating substring
SQL - join and window function

Develop a production-grade application in Python that analyzes data and provides answers to questions based on the dataset.

Q1. System design and project based questions
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Q2. Scenario-based questions that can help assess how you handle various situations
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Q1. How does Django apply migrations to the database?
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Django applies migrations to the database using the 'manage.py migrate' command.
• Django tracks changes to models and generates migration files accordingly.

• The 'manage.py makemigrations' command creates migration files based on model changes.

• The 'manage.py migrate' command applies the generated migration files to the database.

• Migrations help keep the database schema in sync with the changes in Django models.
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Q2. What is hoisting in javascript?
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Hoisting in JavaScript is the behavior where variable and function declarations are moved to the top of their containing scope during the compilation phase.
• Variable declarations are hoisted to the top of their scope, but not their assignments.

• Function declarations are fully hoisted, meaning they can be called before they are declared.

• Hoisting can lead to unexpected behavior if not understood properly.
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