2020 is the toughest season for job interviews. Many big companies, such as Tencent and Byte, have significantly reduced the number of recruitment opportunities, but the interview threshold is repeatedly high. If you don’t prepare hard, you are likely to be dumbstruck by the interviewer. Today, if nothing else, let’s talk about what I’m interviewing for as an interviewer.

Starting as the head of an e-commerce project and later as the chief architect, I interviewed at least 300 candidates. I can’t say that every colleague who successfully joined the company did particularly well, but most of them did.

Excellent technical background is the minimum assessment requirements. Many friends to apply for the foundation or some, but the scope of knowledge is too narrow. So for the Internet, especially for the e-commerce industry, will focus on what assessment? Recently, I have arranged the assessment knowledge that I often ask myself in these years, no less than 100, which covers many big factories’ compulsory test points, high-frequency points and salary increases. These are also the pit points that developers often encounter in daily projects.

For your convenience, I have classified these points into 5 categories: JVM, mysql, Redis, MongoDB and Dubbo. I have organized the disassembly and thinking about these problems into a PDF, which is not listed here due to space limitations. The need of the students can be at the end of the text to receive, I hope to have some inspiration, harvest.

Here are some interview questions to share with you:

JVM

• Is there a memory leak in Java? Please describe it briefly.
• In 64-bit JVMS, is the length of an int the majority?
• What are the differences between Serial and Parallel GC?
• For 32-bit and 64-bit JVMS, is the length of a variable of type int the majority?
• Difference between WeakReference and SoftReference in Java?
• What does the JVM option -xx :+UseCompressedOops do? Why use it
• How do I determine whether the JVM is 32-bit or 64-bit using a Java program?
• What is the maximum heap memory for 32-bit and 64-bit JVMS?
• What are the differences between the JRE, JDK, JVM, and JIT?
• Explain Java heap space and GC?
• JVM memory region
• Program counter (thread private)
• Virtual machine stack (thread private)
• Local method area (thread private)
• Can you guarantee GC execution?
• How do I get memory used by Java programs? What percentage of the heap is used?
• What is the difference between a heap and a stack in Java?
• Describe how the JVM loads class files

mysql

• Database storage engine
• InnoDB (B+ tree)
• TokuDB (Fractal Tree- Nodes with data)
• MyIASM
• Memory
• What are the database engines
• Differences between InnoDB and MyISAM
• The index
• Common indexing principles are
• What are the three paradigms of databases
• 1st NF – columns are non-separable
• Second Normal Form (2nd NF- Each table describes only one thing)
• 3rd NF- No transitive dependencies on non-primary key columns
• Databases are transactions
• SQL optimization
• Explain the differences between DROP, DELETE, and TRUNCate
• What is a view
• What is inner join, left outer join, right outer join?
• What are the problems associated with concurrent transactions?

Redis

• What is Redis?
• How is Redis different from other key-value stores?
• Redis data type?
• What are the benefits of using Redis?
• What advantages does Redis have over Memcached?
• What are the differences between Memcache and Redis?
• Is Redis single process single thread?
• A stringValues can beWhat is the maximum storage capacity?
• Redis persistence mechanism
• Cache avalanche, cache penetration, cache warming, cache update, cache degradation and other issues
• What is hot data and cold data
• Why is single-threaded Redis so fast
• Redis data types and usage scenarios for each data type
• Redis expiration strategy and memory flushing mechanism
• Redis Common performance issues and solutions?
• Why are Redis operations atomic and how are they guaranteed to be atomic?
• Redis transactions
• What is the persistence mechanism of Redis? What are their strengths and weaknesses?

MongoDB

• What is mongodb?
• What are the features of mongodb?
• What do you mean by NoSQL database? What is the difference between NoSQL and RDBMS directly? Why use and not use NoSQL databases? What are the advantages of NoSQL databases?
• What are the types of NoSQL databases?
• What are the basic differences between MySQL and MongoDB?
• How do you compare MongoDB, CouchDB, and CouchBase?
• What makes MongoDB the best NoSQL database?
• Does journal playback have problems with incomplete entries (such as one that happens to fail midway)?
• What is the role of profilers in MongoDB?
• What is a namespace?
• If a user removes an object property, is the property removed from the storage tier?
• Can log features be used for secure backup?
• Is null allowed?
• Update operation immediately fsync to disk?
• How do I perform transactions/locks?
• Why is my data file so big?
• How long does it take to enable backup failover?
• What is master or primary?

Dubbo

• Why Dubbo?
• What are the layers of Dubbo’s overall architectural design?
• What communication framework is used by default, and what other options are there?
• Is the service invocation blocking?
• What registry is commonly used? Is there any other option?
• What serialization framework is used by default, and what else do you know?
• Service providers can implement invalidationKicked outHow does it work?
• How does the launch of the service not affect the old version?
• How to solve the problem of long service invocation chains?
• What are the core configurations?
• What protocol does Dubbo recommend?
• Can a service be directly connected to multiple registrations of the same service?
• Flowchart service registration and discovery?
• How many options are there for Dubbo cluster fault tolerance?
• Dubbo service degraded, failed to retry what to do?
• What are some of the problems with Dubbo?
• How does Dubbo Monitor work?
• What design patterns does Dubbo use?

Conclusion:

To summarize some of the big factory interview questions, need friends can pay attention to wechat public number [Java programmers gathering]

The documentation also includes spring bucket, Mybatis, MySQL, JVM and other topics of technical points, hope to help you sprint gold 9 silver 10.