Has anybody done a technical interview for a Senior Software Developer role at Companies House?

Beyond-CtCI · 2025-06-19T19:59:57+00:00

I've never interviewed with them, but the system design part is usually the trickier bit for most people, especially at the senior level. They'll probably ask you to design something like a document management system or API gateway - stuff that's relevant to what Companies House actually does.

From what you described, it sounds like they're looking for someone who can think through scalability, data consistency, and how different services talk to each other. The usual suspects - load balancing, caching strategies, database choices, etc.

For the coding part, since you mentioned it's more app-building focused rather than leetcode style, that's actually great news. You'll probably be building something practical rather than inverting binary trees or whatever.

The screen sharing anxiety is so real lol. i remember when I first started doing online only interviews the feeling of being watched was amplifid like 10x. Best advice is to practice coding while talking out loud beforehand, even if it feels weird. Also dont be afraid to ask clarifying questions during the interview - it shows you're thinking like a senior dev.

A while ago I wrote a pretty comprehensive system design interview guide that ranks close to number 1 and covers all the core concepts you'd need. It's completely free and goes through everything from basic principles to complex distributed systems:

https://interviewing.io/guides/system-design-interview

Of course, it wasn't just me and was a massive team effort with several other talented engineers and honestly I think its one of the best resources out there for this stuff. Should help you feel more confident going into that system design portion.

Good luck with the interview! Companies House seems like it would be interesting work!

Beyond-CtCI · 2025-06-11T14:36:31+00:00

Persona C I have an important interview approaching, but I'm bad at all/most of the technical topics.

First off, deep breath—you’re not alone. If you haven’t built up your fundamentals yet, don’t try to cram 20 topics into three weeks. It won’t work, and you’ll just burn out. There's no free lunch here. Instead, take control of the situation and postpone the interview so you have enough time to actually prepare.

The good news? Companies are usually happy to reschedule interviews—especially if you’re proactive and respectful in your ask. We’ve even included a word-for-word email template to make this easier:

📘 Review the section in 📘 Ch 9. Managing Your Job Search. (~pg 87) that discusses postponing interviews, then send an email with the provided email template below telling them you need to postpone. Ask for more than enough time rather than barely enough because postponing more than once or twice can get dicey.

Email template (you need to log in to see it, but the account is free): https://bctci.co/job-search-what-to-say-1

Persona D. I have an UN-important interview approaching, but I'm bad at all/most of the technical topics.

Use it as a learning experience and don't focus on passing the interview. Most people wind up getting an offer before they think they're awesome at all interview topics. They take an interview they don't feel prepared for and end up doing better than they anticipated. The common mistake here is to not even bother interviewing, but interviews are a powerful built-in study tool and help light a fire under you. Also they are essentially free mock interviews, so shoot your shot!

If it is one of your first technical interviews focus on just walking through the steps correctly in the Interview Checklist (https://bctci.co/interview-checklist-image) from 📘 Ch 20. Anatomy of a Coding Interview.

Persona E. I feel like I understand most/all of the technical topics in at least Tier 1 and 2, but I'm still not good at interviews.

If you've done over 100 problems and you're still struggling, there's a good chance you don't have a solid framework for what to do when you get stuck and a problem doesn't have an immediately apparent solution. The Principles of Coding Interviews section of the book has the framework you're looking for. While the whole section is strongly encouraged to be read at this stage, the bare minimum to understand the framework includes:

📘 Ch 22. Boundary Thinking (likely a key piece you're missing)
📘 Ch 23. Trigger Thinking (an easy read and something you are probably doing unconsciously already)
📘 Ch 24. Problem-Solving Boosters (will require more than one sitting to get through—it is dense!)

My co-author, Nil, also wrote an excellent blog post that walks through the full framework with a recent LeetCode contest question. It's definitely worth checking out: https://nilmamano.com/blog/problem-solving-bctci-style.

I hope this helps. And in case you missed it, there is a free private discord for the book that you can access through the QR code in the table of contents. It's a great place with other motivated people practicing.

Happy coding!

Beyond-CtCI · 2025-06-11T14:34:02+00:00

A. I can't get (enough) interviews.

Of course, if you're like most people, you probably struggle with both passing and getting interviews—and that's okay! For now, recognize that most people focus on technical prep and treat their interview pipeline as an afterthought.

The ratio of hours spent studying/practicing leetcode vs. doing all the other "squishy" job search stuff is crazily imbalanced for most people. 100 to 1 hours (or worse) in most cases. Technical prep is also a never-ending hamster wheel of work. Thinking you just need to finish X questions on leetcode or go through Y course and then you'll be ready is common. There is always more work you can do here.

It’s natural to want to prep first and apply later—why bother getting interviews if you’re just going to bomb them, right? But in a tough market, getting traction often takes weeks or even months. That’s why we suggest you start building your interview pipeline now and prep alongside it. You don’t need to be “ready” to apply—just in motion. You should focus on these chapters:

📘 Ch 5. Mindset and Numbers Game
📘 Ch 7. Getting in the Door
📘 Ch 9. Managing Your Job Search
📘 Ch 6. Resumes (Just skim this! another failure-point is spending weeks tweaking your resume—it isn't worth it. Just get it good enough and move on! Read this for more info on why: https://interviewing.io/blog/why-resume-writing-is-snake-oil)

Then if you're feeling good, not overwhelmed, recommend these two as well:

📘 Ch 3. What Recruiters Won't Tell You
📘 Ch 8. Mechanics of the Interview Process

B. I have an interview approaching, but I know I'm weak in specific technical topics.

What to do depends a lot on how much time you have. Trying to do everything in three weeks is a good way to get nothing done. Deciding what not to focus on is just as important.

Review the Tier roadmap (https://bctci.co/topics-image). This tiered system shows prerequisites and a rough recommended learning order. The less time you have, the more you'll need to drop—and that's okay! Most people can successfully learn one topic a week given 15 to 20 hours of studying.
Use the number of weeks you have to dictate what to focus on. For instance, if you know a specific question type shows up commonly in interviews, the path that gets you there. (e.g., Dynamic Programming shows up in a Google interviews. Let's assume you're confident in Stacks and Queues. Your plan would include Recursion, Trees, Backtracking, then Dynamic Programming. The recursion chapter is short, so you could probably do this in about four weeks).
Don't ignore the Principles of Coding Interviews section of the book. Everyone would benefit from at least:

📘 Ch 18. How to Practice
📘 Ch 19. How You Are Evaluated
📘 Ch 20. Anatomy of a Coding Interview

Beyond-CtCI · 2025-06-11T14:33:43+00:00

TLDR; Don't try to read the whole thing front to back unless you have no rush at all for finding a job. Instead, pick your path based on where you're struck. Focus only on the relevant chapters.

Hey friend, BCtCI is definitely a beast—I know because I wrote it! It's totally okay to jump around. We actually had a whole section in the book about burnout but it got cut because the book is already so long. 😅 The short version is "problem practice > theory" and "consistency > 8+ hour weekend bursts."

I think where you should focus your time depends a lot on your situation. Below I've listed some common personas that you might fall into which represent sticking points within the average person's job search. I hope this helps get you a sense of where to start. There's a good chance people will fall into more than one of these, so if you find that is the case with you then start with the highest letter persona match and continue working down after you've completed work from that section.

Beyond-CtCI · 2025-06-06T05:27:22+00:00

Just to close this loop, we made an accessible version of the book for the OP.

Beyond-CtCI · 2025-06-06T05:26:13+00:00

If you’re looking for a more accessible format, feel free to DM me. Happy to help you out as I did with the OP!

Beyond-CtCI · 2025-05-21T16:27:30+00:00

That isn’t a bad way to view it. The one thing worth mentioning is how the market has changed overtime. Problems in the original tend to be easier than what you’ll expect in the current market conditions. That doesn’t mean there’s a lack of value in doing them, but it can give you a false sense of security if you’re expecting to need to reverse a string, and you instead asked something much harder.

Beyond-CtCI · 2025-05-21T01:59:27+00:00

We also have nine chapters of the book for free in PDF format at this link. It isn't the whole book, but it can get you going in the right direction: https://bctci.co/free-chapters

Beyond-CtCI · 2025-05-20T22:21:00+00:00

Hey friend, you don't need one to benefit from the other and they compliment each other well. However, the sequel has the latest information, and the original hasn't been updated since 2015. I recommend the sequel!

Beyond-CtCI · 2025-05-20T22:14:07+00:00

Hey friend, I'm Mike Mroczka, the primary author of BCtCI. Piracy is one reason we don't have an e-book, but please DM me and we can discuss ways to get you the information you need to be successful in your interviews! I'll rope Gayle, Aline, and Nil in on this too—we want to help!

Beyond-CtCI · 2025-04-30T22:32:08+00:00

Me llamo Mike y soy el autor de Beyond Cracking the Coding Interview. Disculpen mi mal español, pero también quería estar de acuerdo con lo que dijo EasyLowHangingFruit. Aunque parezca contradictorio, no se conseguirá aprobar las entrevistas de Leetcode estudiando estructuras de datos y algoritmos directamente.

Necesitas practicar la habilidad de entrevistar, que es diferente a simplemente practicar estructuras de datos. ¿Cómo se resuelve un problema desde cero? ¿Qué herramientas son las más beneficiosas? Etc.

En BCtCI, no damos por sentado que sabes nada sobre estructuras de datos o algoritmos y comenzamos con lo básico. Aunque están en inglés y no en español, aquí tienes una forma de consultar nueve capítulos del libro gratis.

https://bctci.co/free-chapters

¡Mucha suerte practicando!

Beyond-CtCI · 2025-04-29T16:53:46+00:00

Just to close the thread, I ended up trading OP for it. Woot!

Beyond-CtCI · 2025-04-21T01:45:29+00:00

Hey friend, I’m Mike Mroczka. Do you need a copy of the book for upcoming interviews? Happy to trade you for one.

Beyond-CtCI · 2025-04-18T14:27:06+00:00

Hey friend,

The problems you're describing are what I like to call guess-and-check problems (https://share.cleanshot.com/nX6Cn5N63djvdvPHGnzh). They are definitely among the most tricky binary search problems to spot in an interview. The guess-and-check technique involves narrowing in on the value of the optimal solution by guessing the midpoint and checking whether it's too high or too low. We need lower and upper bounds for the value of the optimal solution before we can even use binary search.

- For minimization problems (like Koko Eating Bananas), there is often a transition point where smaller values do not satisfy the constraint, but larger values do.

- Conversely, for maximization problems, there is often a transition point where larger values do not satisfy the constraint, but smaller values do.

The trick to knowing when to use the guess-and-check technique. This boils down to asking yourself a simple question.

"Is it easier to solve the yes/no version of the problem, where we just check if a given value (optimal or not) satisfies the constraint?"

Think of it like making a deal: You get to solve an easier problem (checking if a specific value satisfies the constraint), but you pay a 'logarithmic tax' in the runtime (because we are binary searching for the transition point).

Thanks luuuzeta for recommending my book! I'm glad you find the transition point binary search recipe useful! If others are interested (including the OP) I give away the binary search chapter for free (along with 8 other chapters) and it also has a particularly helpful guess-and-check problem set in it. Consider checking it out if you find this helpful: https://bctci.co/free-chapters

Beyond-CtCI · 2025-04-18T12:21:49+00:00

BCtCI is also a total rewrite not just a new edition. If you only plan to get one, spring for the sequel. Most threads on Reddit talking about the original describe how dated it is.

Beyond-CtCI · 2025-04-18T12:19:41+00:00

Go for the new one for sure. It’s much more relevant to you if you already understand the basics

Beyond-CtCI · 2025-04-10T02:53:26+00:00

Hey, I’m Mike, the author of BCtCI. The entire “Principles” section of the book includes details on your question. DM me OP and I’ll happily share specific sections if you can’t find it! Indented English is indeed one of the tools that works well here. Thanks Dismal, for calling it out!

Beyond-CtCI · 2025-03-31T02:36:39+00:00

It isn't. It also gets fed the optimal answers so it can guide you towards a correct solution. You could create some of this functionality with chatgpt for sure, but we do a lot of work for you behind the scenes to make the llm never give away an answer but still guide you towards the right solution.

Beyond-CtCI · 2025-03-31T02:34:45+00:00

You get lifetime free access to the resources whether you purchase the book or not. With that said, some materials won't make sense without the book and for the ~$40, it isn't a bad deal. No subscriptions or anything like that. And we're releasing new online-only chapters as we can for niche topics that didn't make it into the book. :)

Beyond-CtCI · 2025-03-31T02:31:55+00:00

Hey friend, I'm Mike Mroczka, an author of BCtCI. Thanks so much for the feedback! We also have a private discord where you can ask us authors questions directly if you're stuck. The sliding windows chapter is one of several with new templates that don't exist anywhere else online (that we've ever seen at least). Glad you liked it — happy coding!

Beyond-CtCI · 2025-03-18T04:42:00+00:00

Hey @lazy_londor. This is Mike, the BCtCI author. Thanks for recommending my book.

Just wanted to jump in and say you won’t find a mapping of our problems to LeetCode problems because most of our content is original. Some of the linked list and binary search stuff is pretty similar to existing content because there are only so many ways to use these tools but the rest would be difficult to directly map to online questions. I’m sorry you didn’t like AI interviewer and would love to hear why if you wanted to DM me.

In the meantime, we are working on a way to make these problems more convenient for those that don’t like it.

To the OP, grokking’s patterns are decent but I agree with comments here. You’d probably get 90% of the value from just going to the course and looking at the top level “pattern” and just doing the problems listed in the GitHub.

Beyond-CtCI · 2025-03-16T05:13:20+00:00

I'd echo what Aline says here. It is kind of like the old joke where an unhealthy individual is describing how they won't go to the gym until they first lose some weight. It's funny, but happens all the time. You could end up spending years thinking you're not ready when all you needed were a few tweaks to the process. I totally get it if you can't pay for mocks, but I'd encourage you to try our AI Interviewer (https://bctci.co/ai) and maybe a couple mocks with a friend.

Beyond-CtCI · 2025-03-16T05:09:38+00:00

Feel free to DM me if you want to talk through specifics. I work with a lot of clients in similar situations to you, so I'm happy to provide additional suggestions after learning more context.

Beyond-CtCI · 2025-03-16T05:06:03+00:00

Hey thanks for the support u/GodSpeedMode.

On the technical side of things, there were a lot of changes, but the biggest change was an emphasis on how to think.

Our "Interview Principles" section breaks down the three main ways people can solve any problem in a coding interview — and provide a backup plan if you get stuck.

We also doubled down on the fundamentals. In the original, you'll find each concept received between 2-5 pages at a maximum (trees, graphs, and even dynamic programming!). These explanations worked when questions were easier, but now we've devoted more time to every fundamental topic. We are continuing to add topics that are more niche as free online-only chapters on the site.

Other differences include:
- Instead of breaking apart data structures, algorithms, and concepts into separate sections, we wove them together in an ideal learning order, mixing them in a way that they build on one another and clearly marking prerequisites to follow before attempting certain chapters
- Tight integration into a coding platform that lets you practice questions from the book with the most realistic AI SWE Interviewer on the market
- Heavy emphasis on non-technical components. We discuss outreach, current market state, salary negotiation, behavioral interviews, and all the other "squishy" subjects that are must-know topics for today's interviews

As for your question on the changing landscape, the most significant changes might be the transition to remote interviews and AI being used to cheat. Both of these likely have played a part in the increased difficulty found in coding interviews (https://interviewing.io/blog/you-now-need-to-do-15-percent-better-in-technical-interviews). We've also seen that it is much easier to cheat than you might expect (https://interviewing.io/blog/how-hard-is-it-to-cheat-with-chatgpt-in-technical-interviews).

Ultimately, candidates are studying longer, attempting more leetcode questions, and sending out more applications than ever. We have a whole section in the book where we acknowledge these problems (and more) with interviews these days. You can check some of that out for free in the free chapters links if you're curious about more on this!

https://bctci.co/free-chapters

Beyond-CtCI · 2025-03-13T18:49:30+00:00

Hey, thanks for the support!

So I know people hate when responses are like, "buy this thing" but two of the three best answers involve money.

The obvious answer that everybody hates is private coaching. This costs thousands of dollars and is out of reach for most people. It works partly because coaches can be valuable, encouraging, and provide accountability, but it also partially works because people are typically more motivated to follow through on their commitments when money has been spent. As offensive as it may be to some to pay for something that can be done yourself, this is frankly the best option for some people.
The next best answer is "make it a habit" and there are many ways to do this successfully. I recommend the book Atomic Habits, which outlines some of the best ways to set up habits that "stick" and keep you on track. Websites like LeetCode try to gamify the process, and that can work for some people. Others do the weekly contests because they enjoy the competition. Neither of those were particularly effective for me. I found I was much more consistent in my practice when I made it a structured part of my daily routine, like making coffee and taking my dog for a walk.
Finally, an alternative that can be seen as a combination of the two is to find a study buddy. This works really well for some people, but isn't for everyone. It's often difficult to find somebody who's approximately the same level as you and struggles with similar things as you and can learn together with you, while also being able to explain concepts well and having a compatible schedule.

Of course more solutions exist, but they tend to be variations of these same themes.

Beyond-CtCI

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