DEV Community: Daniel

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Daniel — Mon, 14 Nov 2022 23:58:42 +0000

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I explained how I built it here

System Design: Stock Exchange

Daniel — Wed, 05 Oct 2022 10:33:04 +0000

How would you design a Stock Exchange meant to operate at scale?

Estimated Usage

500 million order per day
Uniform usage throughout the day
200 listed companies on the market
1:1 Buy to Sell orders

Functional Requirements

Users should be able to put in orders to buy or sell
Users should be able to cancel orders
Buy orders should be matched to sell orders with the same price if they exist
User accounts have a balance where they have to preload funds in order to place a buy order
User should be able to check the current price

Nonfunctional Requirements

99.999% reliability
Price checks need to be updated within 3000 milliseconds

Try to submit your solution on LeetDesign, share the link in the comments and I'll give you feedback on how you did!

How would you design an Instagram-like backend?

Daniel — Thu, 29 Sep 2022 12:49:16 +0000

📸 Instagram has roughly 500m Daily Active Users

When designing a system to support that scale there are special considerations that need to be made.

How would you design an Instagram-like app to support 500m DAU?

Try out the newest problem we launched on LeetDesign Share a link to your submission in the comments and I'll give you feedback on how you did!

https://leetdesign.com/problems/instagram

Search Engine - System Design optimal solution

Daniel — Fri, 16 Sep 2022 12:09:14 +0000

Search engines are built to help users find relevant resources based on an inputted search query. In our case, our search engine needs to scan, organize and serve relevant urls to users in a timely manner.

Most search engines require us to organize the search data in a way that allows users to quickly get their results, and ours is no exception. The secret to this problem is understanding that we need to preprocess the data to make it more easily searchable.

Functional Requirements

10 relevant results should be returned for each query if they exist
When a user clicks on a result they should be sent to the page
A "good match" is when a url contains a specific keyword
Searches can only consists of a single keyword
All grammatical tenses should map back to the same base words
All "stop words"( a, an, you, or ,etc.) should not be included in the index
Urls should be checked daily for updates
Urls do not need to be ranked off of any relevancy

How would you design this system?

Optimal Solution

Design a movie ticketing application

Daniel — Tue, 30 Aug 2022 04:11:39 +0000

We just published a new System Design Interview practice problem on LeetDesign!

You can check it out here

Prompt
Design an online ticketing system where users can browse whats available and purchase movie tickets

Functional Requirements

Users can see theatre's and times for chosen films
Users can stand by assuming quite seats could open up from cancellation
Users can book tickets from the client
Films should be filterable by city
Users should be able to purchase additional seats after initial purchase

Nonfunctional Requirements

Financial transactions need to be secure
Data must be stored for 5 years
Must not sell the same ticket to more than one user

New System Design Problem: Dropbox

Daniel — Wed, 24 Aug 2022 05:50:32 +0000

9/100 Days of posting new system design problems 🔥

Sadly, I missed yesterday due to some violent food poisoning but after 24 hours of sitting in bed and drinking water, I'm back at it!

You can learn a lot about how big companies work by studying their infrastructure, and Dropbox is no exception!

Give it a whirl and lmk what you come up with

leetdesign.com/problems/dropbox

System Design Practice Problems

Daniel — Tue, 16 Aug 2022 08:16:10 +0000

Just kicked off a new list of system design practice problems!

Problems so far:

Chat system
Tiny Url
Search engine

Give them a shot and send me your diagrams on twitter!
https://leetdesign.com/

Best Engineering Blogs for tech companies

Daniel — Thu, 30 Jun 2022 20:32:23 +0000

When studying for system design interviews, it is always helpful to understand the companies system and how they work. This means looking into their engineering blog and getting familiar with what they are currently working on.

Instead of having to search for each companies engineering blog, I put together a resource that not only links each tech companies blog & RSS feed, but rates the quality of the blog. I share 1-5 stars based on the quality of the content, frequency of posting, engineering deep dives, RSS feed, organization, and graphics.

Check it out here: https://www.hackpack.io/engineering-blogs

Let us know if you have feedback or think we are missing any good ones!

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Looking for a study partner? Hackpack is the most active community of engineers studying for programming interviews. We hold each other accountable, provide support, and fight burnout to study more efficiently and get the job faster.

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VR Mock Coding Interview - Coding Interview - Longest Palindromic Substring

Daniel — Wed, 29 Jun 2022 15:59:52 +0000

Verdict: Pass
Score: 5/5

Coding: 5
Communication: 5
Problem Solving: 5
Inspection: 3
Review: 5

Leetcode #5 - Longest Palindromic Substring (https://leetcode.com/problems/longest...)

The candidate did an excellent job. He had seen the problem during his practice, but was still able to explain the details of an optimal solution and bring the interviewer along for the ride. He coded the solution fluently, and reviewed thoroughly. Excellent work.

What they did well

Able to code the optimal solution quickly
Explained his thinking
Drew out an example and walked me through it
Was able to deduce the runtime and space complexity confidently
Handled questions from the interviewer really well

What could be better

Nothing significant that needed to be improved on.
As an interviewer, I would have loved to see more of the problem solving process involved with coming up with the solution with more questions about the inputs and outputs. But since the candidate was able to so clearly articulate the solution I disregarded this.

Check out the full interview: https://www.youtube.com/watch?v=Aiw3m8EK0rs&t=179s

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Are you ready for your FAANG Interview? - Free Quiz

Daniel — Tue, 28 Jun 2022 17:18:28 +0000

Gauging how prepared someone is for a big tech interview is a tricky thing to do. There are hundreds of questions an interviewer could ask and they have complete control of which one they chose. You could get something random that has never been asked before, which can make preparation seem impossible.

The good news is that most interviewers behave within a certain bounds. This means you can prepare and have a 90%+ chance of being ready for it. So while nothing is 100%, this quiz includes the same general questions that I ask the Hackpack community to gauge if they are 90%+ ready for their interview.

After you take the quiz, you will be emailed with a % score on how ready you are for the interview! Enjoy!

Link to Quiz: https://www.hackpack.io/ready-faang-interview

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The Big Tech Coding Interview Framework - Pt 4. Review

Daniel — Mon, 27 Jun 2022 13:46:20 +0000

This is the 4th part of a four-part series. For those who want to jump ahead, here is a link to the entire framework. In addition, if you want to read the first three parts, they can be found here: first, second, & third.

Review

Now that you have inspected the problem, created a strategy, and coded, all of the hard work is essentially over. The final step is to make sure you review your code. Even if you have only a few minutes at the end of the interview, you want to review your code to make sure you didn’t do anything wrong. It is also better to catch any little mistakes before the interviewer does. In addition to ensuring that the problem you just coded actually works, interviewers want to see that you are someone who checks their code. Working at one of these Big Tech companies means you are sometimes impacting billions of people with your code. Interviewers want to know that you are not someone who ships out bugs.

In the absolute worse case, If you don’t have any time at the end of your interview, make sure you are at least pretending to try and review what you did before your time is up. This isn’t something you should really bank on doing but if you are down to the wire and still want to make it clear you check over your work, just try to go through the motions.

Do not ask “Am I done?”

Do not ask an interviewer “Am I done?”. It shows a lack of confidence in the work that you are doing. Instead, when you think you are finished, immediately start running through one of your input examples. If you followed this framework correctly you should of already explicitly stated what the input and desired output was and drawn up an example (done in step one: inspection)

In addition, there are a few things that you can run through to review your code that we will review in this article.

Questions to ask

Did I prove my runtime complexity?

You should look at the solution you wrote and make sure that it matches the runtime that you stated as you were strategizing. Compare them directly. If you have the time, go through your code and explain the performance of your code in depth.

Did I prove my space complexity?

You should do the same here but for space complexity. Look through the solution you wrote and make sure it matches the space that you stated out as you were strategizing. You can also go line by line and show that some lines incur constant space while others are more expensive.

Did I write up different test cases and process them?

After you try testing your input example, run through a few additional test cases. Start simple and get more complex.

Did I go line by line no matter how trivial?

Did you read through what you actually wrote? Did you read through every line in your function and make sure that it actually does what you think it does? Do you have any ‘off by one errors’? Is your syntax correct? After 30 stressful minutes of inspecting, strategizing and coding under pressure, it can be easy to forget a semicolon. Take it slow if you can and work line by line to make sure nothing is off. You don’t want your interviewer calling out some small error you missed because you were moving too fast.

Did I have to make any changes when reviewing my code?

This is more for your own personal reflection. If you are making the same mistakes and changing the same piece of code every time you do a problem, it should be called out and addressed. For example, if you are always having off by one errors when doing binary search, recognize that. Keep yourself honest here. The more you learn from your frequent mistakes the more you will grow.

If you have time

In a perfect world, you would have time to run through each of these questions at the end of the interview. You would test your code and ensure it is perfect before you finish. The reality is, sometimes you are running short on time and by the end of the interview you feel like there is no time to review.

Even if you only have a few minutes, it is super important for the interviewer to see that you are someone who checks your code. For a lot of interviewers this is just a box they need to check for them to know that you aren’t someone that will send bugs to production.

Conclusion

If you have the time, check your code! If you followed the framework correctly, this should be a super simple run through. Feel proud of yourself once you have finished this step! You can now apply a simple framework to attack every programming interview. This should fuel your confidence and allow you to enter your interview knowing you can handle anything that they throw at you.

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Identify Where you are Uncomfortable and Lean into it

Daniel — Sat, 25 Jun 2022 13:52:56 +0000

It took me two months to open a JSON file. I didn’t know anything about them and every time they came up at work I would avoid being involved in the conversation. I had a mental block that came up every time I heard someone say “check the JSON” file. It wasn’t until I accidentally opened one that I realized how simple they were. I can’t believe it took me that long to even try to learn what they were facepalm.

The real lesson here is that avoiding a topic because it makes you uncomfortable can hinder your progression. The sooner you lean into what makes you uncomfortable, the faster you will grow as a software engineer. As they say at Replit: “seek pain”.

Anyone else have a similar experience?

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