preface : Ali is actually where I want to go , yesterday offer call Yes . The Department is new retail . Make a wish offer.

In fact, I'm almost over , Just three places : Ali , tencent , Meituan . Tencent and meituan have got it now Offer, Ali is still waiting . Throughout all interviews , In fact, I feel that there are two things that are most helpful to me , The first is algorithm capability , This makes it easy for me to tear the code in the written examination or the interviewer , Basically no problems , It's all a second . The second is the internship experience , I've learned a lot in English , I've seen a lot of new technologies . Resumes from other companies have also been submitted , Some also invite written tests , such as pdd, Kwai Fu . This hasn't started yet , The Buddha system follows suit . Join us when you are free , If you don't have time g Yes .

1. one side .

(1) self-introduction

(2) Talk about the difficulties in the project ?

(3) In your service qps How much is it ?( This is actually quite big , There are tens of millions )

(4) How to solve high concurrency ?( From load balancing to storage )

(5) I heard you say that back-end storage is MySQL+Redis. say something MySQL?

(6)MySQL How to realize master-slave synchronization ?

(7)MySQL Indexes ?

(8) What is the impact of modifying the primary key ?

(9)Redis avalanche / breakdown / Concept of penetration ?

(10) How to solve these problems ?

(11) Can you tell me Redis Common architectures ?

(12) Distributed cache consistency, you know ?

(13) uniformity Hash Algorithm talk ?

(14) Do you understand the operating system

(15) Can you talk about deadlock

(16) Deadlock resolution ?( Conditions for deadlock generation , prevention , Release, etc )

(17) I heard you just now , Can you talk about this algorithm

(18) What do you want to ask me ?

2. Two sides

(1) self-introduction

(2) Look at your resume Kafka,Rocket MQ ,nsq etc. , Can you say that ?
(3) Talk about the selection of message queue in your project ?

(4)Kafka Reasons for high throughput ?

(5)Kafka Have you done it for flow computing ?

(6)Rocket MQ Why is it often used in online business ?

(7) I heard you just now tag filter , Can you tell me what this is ?

(8) Why are you from nsq Migrate to Rocket
MQ?( How do I know that , The company pushed everyone to move .... But at that time, fortunately, a big man spoke , I listened , Said a few important points , Mainly nsq Dual computer room disaster recovery )

(9) Multithreading understand ?

(10) say something synchronized keyword ?

(11)wait/sleep Differences between ?

(12)nitify/notifyall Differences between ?

(13) How threads are created ?

(14)callable Advantages of ?

(15)future Has the interface been used ?

(16) There are several thread pools ?

(17) Which one do you usually use ?

(18) Talk about common rejection strategies ?

(19) Lock, you know ?

(20) What is a spin lock ?( Finally, I talked about adaptive spin lock )

(21) Optimistic lock in JDK Where can I find it? ?(ConCurrentHashMap There are )

(22)JAVA of GC?

(23)GC algorithm / Garbage collector / Generation recycling

(24) frequently Full GC How to deal with it? ?

(25)Linux Do you understand ?

(26)IO Model talk ?

(27) How is multiplexing implemented ?

(28)epoll Must be better than select/poll Efficient ?( not always , The number of active connections should be considered )

(29) View current cpu Command of status ?(top I know this one )

(30) see tcp port ?(netstat -t )

(31) Micro services understand ?

(32) What does service registration discovery mean ?

(33) Can you talk about the concept of fuse ?

(34) Can you talk about the common fusing algorithm ( An algorithm based on water drop funnel is proposed )

(35) What do you want to ask me ?

Tell the truth on both sides , The body is hollowed out . I asked almost everything I knew . It feels like it's bottoming out . And then we finished without an hour , Just check it .

3. written examination .

After the interview, he was asked to take a written examination , Two programming questions .

(1)N Individual election i Make up a team , From here again i Choose a captain , How many options are there ? This question is very simple . That's it :


This summation is simple , The answer is :


As for why , Simple reasoning , Consider binomial :


Take the derivative of this binomial , Then you'll find the results . Final order x=1 That's the answer . This was done directly in my mind , Not before and after 30 second . This problem requires a fast power , Probably 3 The first question is seconds in minutes .

(2) A search +DP. I wrote one bfs+dfs+dp . Yes 100 Multiline reluctance AC.

4. Code evaluation

I thought it was gone after the written examination , Then we have to evaluate the department code . Four questions . I can't remember the two algorithm problems clearly , Because it's simple . Two more JAVA Multithreading .

(1) Alternate printing with two threads 1-100 The numbers inside , An odd number an even number .

(2) Write a simple multithreaded network program , This is a short answer , It's based on TCP Synchronous blocking method , Finally, I said it can be used JDK of NIO Frame or encapsulated Netty Can be implemented efficiently .

5. Three sides

(1) self-introduction

(2) What did you do at school ?

(3)JAVA How much did you learn ?

(4) Have you understood the framework ?

(5) Can you tell me Spring Inside IOC Do you ?

(6) What does dependency injection mean ?

(7)AOP And ?

(8)Spring AOP Underlying implementation of ?

(9)Proxy Class Invoke What do you mean? ?

(10) Tell me about your understanding of callback ?

(11)Spring Boot Do you know ?

(12) Tell me about it and Spring Differences between ( Fortunately , Because I really haven't used it , Only know the difference )

(13) Is there an Internet connection

(14) say something TCP Three handshakes ?

(15) Four waves ?

(16) Why TIME_WAIT?

(17) Will packets always loop in the link ?( can't , There's one ttl)

(18) Tell me about your project in bytes

(19) How do you implement server push ?( Said a WebSocket How to do it , Actually, I didn't do much of this )

(20) How much data do you have ?

(21) How to improve throughput ?

(22) I just heard from you Faas? Can you tell me what this is ?

(23) say something IAAS,PAAS,SAAS?

(24) What do you think Faas This thing ? What's the improvement from the previous one ?

(25) Listen to you just now Faas The upstream delay is actually very high , How .( This is nonsense , In fact, I usually shield the delay alarm ....)

(26) What do you want to ask me ?

The three sides actually had a very comfortable conversation , After the interview, I checked it and passed it directly .

6. Four sides

(1) self-introduction

(2) Tell me about your project in bytes

(3) How does permission control work ?

Here we are , I introduced it xxx, then xxx, last xxx.

The interviewer asked a question , His problem doesn't seem to me to be a problem , Because this can't happen . I didn't get To his point , Always bbll This thing , yes 10 More minutes ..... It ended up nothing . Because I told him , This will not happen , It is intercepted when it appears in the middleware part , It won't hit me . He insisted that it was not safe , Ask me how to solve it , I said I would add another layer of authentication logic .... And then we bbll It's not over .

(4) ok , Actually, you didn't make it clear . Change the subject .JAVA How are you doing ?

(5) Tell me about your understanding of threads .

(6) Synchronization between multiple threads ?

(7)synchorized and Lock Differences between

(8) Can you say something JVM of synchronized Do you support it

(9) How many collection classes have been used ?

(10)HashMap Implementation of ?

(12) Thread safe ? It's not safe. What's safe ?

(13)HashTable and HashMap Differences between ?

(14) What design patterns have been used ?

(15) In which application scenarios will the singleton be used ?

(16) How to ensure the thread safety of a singleton ?

(17) How is observer mode implemented ?

(18) Talk about the application scenario of message queue .

(19)Rocket MQ Characteristics of ?

(20) Why is it commonly used with online business ( Low delay )

(21) I usually read those books ?

(22) How long can I practice , when does it start? ?

(23) What do you want to ask me ?

The four sides are finished. I don't feel it anymore .... Because I finally asked the interviewer what points he valued in the interview , He said his understanding of the problem , See if you can explain it clearly , Isn't it clear that I have some questions ? feel gg

  After a few days , Did you check or did you pass .

7.HR noodles .

Talked a lot , From high school to college and the future . Why study computer ? Why go to this university ? ok , Pretty good .

8. yesterday Offer Call Yes .

Ali, the interview is over , It's not easy to have a look .