Facebook/Meta Network Production Engineer

Time for me to give back to society which helped me, if you are benefitted, please share your experience when you can after your interview :)

2024 Meta Interview experience

Network Round Screening ~

1. This question is always asked - what happens when you type facebook.com in browser
   Ans - Concepts to discuss - DHCP for locap IP, dhcp gives default gateway, ip/subnet for our laptop and local DNS, DNS query IS generated, ARP concepts in local lan, response for DNS most probably cached in between, routing
2. Switching concepts - what happens if a layer2 dest mac is not found in switch
   Ans - It will broadcast to all ports except incoming one
3. Dhcp 4 way handshake, follow up questions were asked
4. TCP - handhsake, tvcp connection closing - follow up what if server does not ack your closing request, how is reliable transfer maintained - ans using seq and ack no (detailed follow ups)
5. Routing outcome- how is routing table look like, how router preferences routes over other learnt routes - ans - read around IP specificity, Administrative distance, path metric, etc

Round - pass

Coding screen -

1. Invalid parenthesis
   Given string such as (ap[)
   tell if string has valid parenthesis
   ex - ()ap[]
   ans - valid
   ex2 - Pa([)
   ans - invalid since for any open brace, its corresponsing closing brace should come first for ex Pa([]) is valid
   ex3 - (([])} - ans invalid ) was expected
   ans - use stack

2. Infamous dinosaur q
   given two csv files with 2 properties as 2 columns and one column as dino name in each csv file (2 properties in each file)
   Print 5 fastest dinos - speed is calculated using a formula using all 4 properties

Round passed

Finals stage -

1. Behavioural
   Current work exp, past work exp, different situational qs
   Most important they will always ask why meta? what do you know about Production eng role? Be prepared to use all links provided in study prep to structure your ans
   Give all behavioural and to tick metas value - ex tell me a time when you had conflict with someone? ans - I proactively pushed code speed up in same ticket thinking about long term impact, but in my management you should create seperste ticket for each task, so I learnt I should have created new ticket and done that task. They will like this and since its fast speed, product ownership etc

Round - passed

2. Network -
   a. What are physivsl componenets of router - i struggled here but should have said something about buffers, NIC cards - bad impression
   b. IN depth all components of TCP and follow ups - pass
   c. When a packet is sent from A to B, tell all the headers in every layer ad much you can, he even asked for http headers which I said i was not prepared. Follow up - which of header values do you think would have changed when host b recieves - ans - IP checksum in layer 4 would change, DEST MAC add in layer 2 will chsnge hop to hop - pass
   d. Bgp - how does bgp internal perr prevent loop - i failed here
   e. how would you trouble shoot a slow network and tools you may use when sending from host a to b over internet for ex - i failed here as well, simple sns ping, tracert, ping stats not enough
   overall - round fail

3. Coding -
   a. if a string is palindrome or not
   b. Given a file containing messages with multiple lines, each ending with new line and %

for ex -
message number
one
%
mess
no
2
%
one line mess
%

when the program is run - you have to print a random message ensuring randomess is equally among diff messages
you can use inbuilt random fucntion

follow up - Space complexity - O(1)
follow up - can you solve if you can only read certain chars at a time.
final follow up - you use hashmap with index as key and seek byte stream as value

round passed

4. network design
   most toughest and weirdest interview.
   Told interviewer i have no exp in designing, and know basics. I think it is very imp to discuss and trll about yourself to interviewer so he can understand your past exp and situation, or else they dont know much about you and may ask unnecessarily tough qs which younwont know.

how would you arrsnge 100 servers for a company and lets say 4 racks. i said whatni had crammed in topology - access, distribution and core layer.
follow up - lets say you have 100mbps link, do you think you sre utilising bandwidth equally. i said layer 2 sto will block so I will use ip instead so i can utilise losd balance.
Ospf to use since you can load balance based on bandwidth cost.
Indid mistake of mentioning NAT somehwere out of confusion, which led him to think I am not dure what is NAT, but i had said it out of conufion while thinking somethign. As interview ended, i realised there is no need for NAT.
round - fail

overall - fail