Tech Interviewing

Different aspects of the job: Project delivery. Big picture thinking. Could be both vision or strategy. Mentorship. Different skills they need: Technical skills. Product management. Project management. People skills: how to organize people to work as a team, grow their careers etc. Different archetypes, i.e. style of work they do: Team lead: usually a starting point for a Staff engineer, something they transition into from a senior engineering role. Architect. Solvers: usually present in teams that place more emphasis on individual contributions than on teams. Right hands: borrow power from and act as proxies for senior leadership.

Speak slowly. Pause before you respond to anything. Story telling tips (for behavioral rounds): STAR technique - very important. In most cases, the technical details (of the situation or actions) don’t matter too much, so no need to delve into those unless cross-questioned. As for actions, try to answer in numbered bullet points: I did 3 things: One, … When asked a question, pause a few seconds and think what the actual underlying question is or what exactly the interviewer is looking for. For example, a binary question doesn’t need to be answered by a yes/no. Some behavioral questions require you to show how you collaborate. So, talk about 2-3 stakeholders you worked with to answer those. (Escalation should be the last resort: don’t bring it up unless absolutely required.) Phrases to use: One of my teams. But … therefore. (Conflict and context.) Don’t use and then. Drove alignment. Calculated risk. Build relationships with people. Build trust. I > we. I learnt XYZ from this engagement/project. I collaborated vs I told junior SDE to do X. Bring in engineering perspective by saying something like, I analyzed how the requirement would fit into our current architecture. Project retrospective: ...

Questions to ask if I am talking to a medium sized company: How do you handle difficult decisions? Can you talk about a situation where you changed your company/product direction because of such discussions? What’s the long term vision? Or are you thinking of one?

https://igotanoffer.com/ https://www.hellointerview.com/ https://interviewing.io/ Things to keep in mind: I feel these work well for people interviewing at an SDE-3 or Staff level roles. For more senior roles, such as Senior Staff or Principal, I couldn’t find suitable interviewers at least on the first website above.

I recently gave a few mock interviews. Here’s some feedback I got from those. 1/29: “User flow/experience”. Non-functional requirements. Scale explicitly. Latency. Get easier part and finish it as well. Can help put more boxes on the diagram. Trade offs: focus on that. Proactively find issues and try to get things right in at most 2 passes. 2/3: Capacity planning good. Don’t assume database is a black box - dig deeper. Non-functional requirements. Latency. Availability. Keep updating the diagram as you speak. 2/16 (behavioral): Use examples to answer generic questions. Ask questions for behavioral too. (Gives you time to think too.) Ask questions early. (Very important, and maybe early so that you don’t run out of time at the end.) People like to hear their your own voice. Do some research about the company beforehand. Can help you ask good questions as well. Roughly finish an answer in ~2 mins. (3 mins is too long.) 2/16 (behavioral): About yourself: You can tell about your background etc. so that you can build curiosity. For projects, talk about impact. And what did you learn. Moving fast. Measurable business impact. Scalability. What you learnt: add to every answer. Collaboration important as well. We vs I. Need more direct conflict stories. Co-worker, manager, etc. didn’t agree with me. 2/17 (project retrospective): Dog feeding. Think of metrics. TPS. CSAT. Done better: Lack of expertise == lack of technical gap. “Better job in covering our technical gaps.” Architecture: More complex. Need to speak for 45 mins. Scalability in everything. Use PM, TPM in your stories. 2/19 (behavioral): Shoot for ~3 mins. Story: STAR-L format. L == learning. A -> bullet points.

Scope (of my role at current organization). About me, as an individual: Strengths. Growth areas, in terms of technical skills. Growth areas, in terms of leadership skills. Feedback that surprised you. What inspires me. What drains me. Leadership skills: Conflict with teammate. (Could be an example where you changed your mind.) Conflict with cross-functional team. Conflict with a partner/cross-organization team. Engagement with a partner team that went well. Engagement with a partner team that didn’t go well. Gave feedback to a peer or junior. Handle shift in priorities from leadership. Best mentorship relationship. Situation where you needed crisp communication. Acted in a tense/ambiguous situation where you didn’t have enough data. Some cross-function partner or someone from another organization wasn’t performing well. Manager specific: What do you look for in your manager? Feedback to upper management. Conflict with manager == feedback to manager. Project retrospective (for one large project): What would you do differently if re-starting from scratch? Technical and organizational challenges. (Not the same as trade off.) Technical trade off. Business trade off. Biggest: Technical problem == road block. Risk that paid off == decision that went against popular opinion. Failure == risk that didn’t pay off as expected. Operational event. Operational process you setup. Short-term vs long-term trade off. Something you did for the team that you are proud of.

Number of seconds: 1 day: 100k 1 month: 2.5M Number of users: USA: 300M Social networks (i.e. daily active users): Facebook: 2B YouTube, WhatsApp: 1B. (YouTube hasn’t published its DAU but it’s definitely going to be more than Instagram’s, so 1B should be fine.) Instagram: 500M Snapchat, Twitter: 200M Reddit: 50M Proportion of users who create vs consume: 1% 80-20 rule: 20% things get 80% traffic. So, assume cache rate of 20%. Machine: Number of connections an average modern server can handle: 50k Latency (see more here, ignore other Google search results as the numbers there are outdated): Read 1MB from: Memory: 3 us SSD: 50 us Disk: 825 us Network round trip: Same data center: 0.5 ms Halfway across the earth: 150 ms ID: Assume number of bytes for a string = 2 * length. Assume you use [a-z, A-Z, 0-9] to generate your IDs. Then 62^8 is a huge number that should suffice for most use cases. UUIDs are 16 bytes. Bytes: KB =1e3 bytes. MB = 1e6 bytes. GB = 1e9 bytes. TB = 1e12 bytes. PB = 1e15 bytes.