orange

Project retrospective: 1hr

TODO:

• pick two projects and be able to dive into project details

ACK frequency

• tracking issue: https://github.com/aws/s2n-quic/issues/1276
• cpu increase: https://github.com/aws/s2n-quic/pull/1298
• revert pr with some analysis shows : https://github.com/aws/s2n-quic/pull/1368

RFC:

• Acks uses:
  • progress: acknowledge packet received
  • loss recovery: detect a packet was not received and retransmit
  • cc: regular acks help establish good RTT estimates and drive CC
  • ECN: congestion signal by the network

ACK Frame {
  Type (i) = 0x02..0x03,
  Largest Acknowledged (i),
  ACK Delay (i),
  ACK Range Count (i),
  First ACK Range (i),
  ACK Range (..) ...,
  [ECN Counts (..)],
}

• motivation: expensive cpu to send/recv. asymmetric links like satellite. ack rate can affect link efficiency.
• negotiating the extension: min_ack_delay. the minimum amount of time, in microseconds, that the endpoint sending this value is willing to delay an acknowledgment
• ACK_FREQUENCY frame:
  • Ack-Eliciting Threshold: max ack eliciting packets received before sending an ack
  • Requested Max Ack Delay: max time to wait before sending an ack
  • Reordering Threshold: max number of reordered packet before sending an ack
• IMMEDIATE_ACK frame: asks peer to send an immediate ack
• Expedite ECN: ecn marked packets should not be delayed
• other concerns:
  • congestion control:
  • application limited:
  • burst mitigation: if sending is dependent on recieving acks. use pacing
  • loss detection is hard: RFC doesnt provide a good solution
  • connecion migration: send IMMEDIATE_ACK to expedite path validation. ack frequency is NOT reset!! on new path.. but should be update to the new path

optimistic ack mitigation

• pr https://github.com/aws/s2n-quic/pull/1986
• rfc link https://www.rfc-editor.org/rfc/rfc9000#section-21.4

netbench

Technical: 1hr

Orange cloud: Behavioral: 30 min

TODO:

• pick 5 projects and STAR them.
• read https://www.hellointerview.com/learn/behavioral/overview/introduction

TOP

• A design choice that encured technical debt but you think it was a good choice.
• Tell me about a time you worked well within a team.
  • Helped co-worker in CLOUDFRONT integrate with async cert loading feature.
  • helped deliver quic over 2 years. specifically worked in a team of three to review prs, make design decisions etc.
  • connection migration pentest
  • orchestrator. i implemented the library logic and he helped me with the automated infra
• Tell me about a time you dealt with conflict on a team. How did you solve it?
  • prioritize features for the orchestrator. we met with the stake holder and figured out which features they actually wanted to help prioritize the project
  • • How do you respond when you disagree with a coworker?
      • disagrements usually stem form mis-matched assumptions or lack of communication. so i like to start with having a conversation and trying to understand why there is a disagreemet. usually when this happens we both end up learning something.
• Tell me about a time you failed at work.
  • ack frequency project. the cpu usage went up after implementing the solution
• Can you give me an example of how you set goals for yourself?
  • daily task list. mark what got done and what did not
• Tell me about a time you showed leadership.
  • spoke up about technical decisions that I spoke out on
  • representing someone external to yourself
    • took initiative to fix handshake status. added fuzz testing verify the solution.
    • automate release versioning
    • customer contact list
• Tell me about your biggest weakness.

MID

• Tell me about a time you faced a really hard problem / a challenge at work.
• Tell me about an interesting project you’ve worked on recently.
• Tell me about a time you had to meet a tight deadline.
• Tell me about a time you had to prioritize projects under pressure.

LOW

• What is the most helpful feedback you've ever gotten?
• As a software engineer, you must be both predictable and innovative. How can these traits coexist in your work?
• Tell me about a time you adapted to a new situation or environment.
• Tell me about a time you needed information from someone who wasn't responsive. How did you handle it?

Other

• Why do you want to work here?
• Walk me through your resume and relevant experience.

System Design: 1hr

TODO:

• Watch this video to understand how to structure the solution: https://www.youtube.com/watch?v=fhdPyoO6aXI
• read https://www.hellointerview.com/learn/system-design/in-a-hurry/introduction
• design 2 systems as practice

Executive call

https://blog.cloudflare.com/cloudflare-2024-annual-founders-letter/

One of the most common questions we’re asked is how we plan to preserve Cloudflare's culture? Our answer is always the same: the goal isn't how to preserve our culture, it's always how to improve it.

• It seems to me that CLOUDFLARE is in a crowded market space (cdn/securing the internet (fastly), paas (aws), data security (crowdstrike)). What do you believe is your single biggest technical or non-technical advantage that will make you successful over your competitors?
• What is the top kpi/metric you personally pay attention to, to make sure CLOUDFLARE is maintaining its momentum?
• What is the most imporant thing CLOUDFLARE does to build high-functioning and talented teams?
• AWS's customers dislike that there are over 200 services.
  • In one of you blog posts [1] you mentioned:
  • "we believe our continued success should be primarily driven by new innovation, not by milking old features for revenue."
  • How will you preserve a seamless user experience as you continue to launch new features?

[1] https://blog.cloudflare.com/adjusting-pricing-introducing-annual-plans-and-accelerating-innovation/