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Hello Interview

by Evan King & Stefan Mai · Intermediate · 270K subscribers

Structured walkthroughs and mock interviews that show what interviewers look for.

Recommended in published system design guides

Learn system design with Hello Interview, step by step

55 videos in 5 steps, about 33 h 11 min of watching. Start at step 1 and move down.

  1. 1Start here: the basicsNo background needed. What the main ideas are and why they exist.
  2. 2The building blocksCaches, queues, databases, load balancers: the parts every design is made of.
  3. 3Design whole systems (HLD)Put the blocks together for a real product, step by step.
  4. 4Low-level design (LLD)Classes, patterns and clean code inside one service.
  5. 5Go deeperInternals, trade-offs and how large systems really behave.

Order and levels are picked by us from titles and lengths. The one-line notes are ours. Every video plays from YouTube and belongs to Hello Interview.

Hello Interview’s own courses and series

Playlists the creator put together, in the order they made them.

  1. System Design WalkthroughsA series from the creator, in the order they made it.
  2. Deep DivesA series from the creator, in the order they made it.
  3. BasicsA series from the creator, in the order they made it.
  4. Low-Level Design BreakdownsA series from the creator, in the order they made it.

Latest uploads

What viewers say (5)

Public comments on this channel's recent videos. They are not reviews of this site.

  • How the system design interview goes really depends on the interviewer too... Recently had a terrible experience with an interviewer for a senior role where I got a question for a video streaming service which I fairly had an idea of how to design. I had started out with 3 core requirements, but interviewer kept adding other functional requirements which were mostly extra stuffs like subscription, billing, which I was considering as out of scope. So, requirements section took away a lot of time than expected.. Then later when I was going through high level design , I had sketched out blob storage box, and maybe I had paused for 3 seconds, he mentioned something related to CDN, which I was going to add myself next. Then he made a comment that I need to add these optimization myself and not wait for his suggestion. I straight away knew I wasn't going to pass the interview, which I didn't. Had it been a more co-operative interviewer, I feel I could have passed it

    @ssk5563-b1u· 8 likes

    on

  • System design interviews have become a theatre act. One has to deliver items in a certain way, else you are not good enough

    @swarupmahapatra1· 7 likes

    on

  • so many questions, why orders are stuck, and did you check and confirm them if they were actually shipped before changing them as shipped. also you dont need outbox just for seperating emailservice and orders service, if you think any shipped email shouldnt been sent after X days then put a check on them would be simplier and more robust solution then to put a outbox in between. i think this is solving wrong problem to begin with. also lets say you want to change them to shipped, you can do that by sql update directly, which will not trigger anything else, assuming you dont have a direct sql trigger setup.

    @master-debater· 6 likes

    on

  • Not very good example ig We had this pattern implemented to capture any changes in the old db records within a single transaction. Basically if a record was created or updated, a trigger would fire and insert a event in the outbox table within the same transaction, keep the system (new db) eventually consistent and not losing any data

    @Golfer-xx8vd· 3 likes

    on

  • Followed your videos and cracked offers from 3 companies :) I had never given any system design rounds earlier, your videos had taught me a lot. Thanks <3

    @doodlepoodle-1· 3 likes

    on

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