Redis Interview Questions

Prepare better with the best interview questions and answers, and walk away with top interview tips. These interview questions and answers will boost your core interview skills and help you perform better. Be smarter with every interview.

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Beginner

Redis supports following Data Structures:

  • Strings
  • Hashes
  • Lists
  • Sets
  • Sorted sets with range queries
  • Bitmaps
  • Hyperloglogs
  • Geospatial indexes with radius queries
  • The whole dataset has to be kept in memory - so the space is limited
  • Single threaded
  • It has got limited client support for consistent hashing
  • It has significant overhead for persistence
  • It is not deployed widely

No. Redis compromises with durability to enhance the speed. In Redis, in the case of system failure or crash, it writes to disk but may fall behind and lose the data which is not stored.

Following are the main features of Redis:

  • Redis is very simple to install setup and manage.
  • Redis is very fast. It can execute 100000 queries per second.
  • Redis is fast because data is being persistent in memory as well as stored on the disk.
  • Redis operations working on different data types are atomic so these operations can be accomplished safely i.e. to set or increase
  • a key, add or remove elements from a set or increase a counter.
  • Redis supports a variety of languages i.e. C, C++, C#, Ruby, Python, Twisted Python, PHP, Erlang, Tcl, Perl, Lua, Java, Scala etc.
  • If your favorite language is not supported yet, you can write your own client library, as the Protocol is pretty simple.
  • Redis supports simple master to slave replication.
  • Redis offers simple yet powerful data structures
  • Redis dataset can be persisted on disk to ensure data durability
  • It’s very easy to work with Redis
  • Redis values can contain more complex data types, with atomic operations.
  • Redis is an in-memory but persistent on disk database
  • use BGSAVE command to Save a spanshot of the database into a dump.rdb
  • Copy this dump.rdb file into another server.

Use the following commands:

$keyList = $redis->keys("*");
print_r($keyList);
/*Array ( [0] => tutorials [1] => name ) */

Yes, a common design pattern involves taking very write-heavy small data in Redis (and data you need the Redis data structures to model your problem in an efficient way), and big blobs of data into an SQL or eventually consistent on-disk database. Similarly sometimes Redis is used in order to take in memory another copy of a subset of the same data stored in the on-disk database. This may look similar to caching, but actually is a more advanced model since normally the Redis dataset is updated together with the on-disk DB dataset, and not refreshed on cache misses.

Operation keys of Redis includes:

  • TYPE key
  • TTL key
  • KEYS pattern
  • EXPIRE key seconds
  • EXPIREAT key timestamp
  • EXISTS key
  • DEL key

For use Redis in .net application need to follow given steps:

  • Download Redis Server
  • Install Redis Server
  • Download Redis Client
  • Set Configuration into Web.config File
  • Use Redis Client Class

To use Redis in .Net applications, follow these steps:

  • First, Download Redis Server.
  • Install Redis Server.
  • Download Redis Client.
  • Set Configuration into Web.config File.

Use Redis Client Class.

Advanced

Below are few main reasons that Redis is different when compared to other key-values store databases.

  • Redis being an in-memory, it is persistent on disk database, thus very high write and read speed is achieved with the limitation of data sets that can't be larger than the memory.
  • Redis is a different evolution path in the key-value DBs where values can contain more complex data types, with atomic operations defined on those data types. Redis data types are closely related to fundamental data structures and are exposed to the programmer as such, without additional abstraction layers.

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Prepare better with the best interview questions and answers, and walk away with top interview tips. These interview questions and answers will boost your core interview skills and help you perform better. Be smarter with every interview.
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