Top Couchbase Interview Questions (2021) | CodeUsingJava
















Most frequently Asked Couchbase Interview Questions


  1. What is Couchbase?
  2. What is Couchbase server?
  3. What is Apache CouchDB?
  4. What are the features of the Couchbase Server?
  5. Name the elements which are present in Couchbase Node?
  6. How many functional blocks have involved in Couchbase Server?
  7. How can we find and fix a Rails and Couchbase memory leak?
  8. How can we use HTTPS replication with iOS Couchbase Mobile?
  9. What are the 4 subsystems which function on every node?
  10. How to merge data in Couchbase with map reduce?
  11. What is a Bucket in Couchbase?

What is Couchbase server?

Couchbase is an open source, document oriented and is multi service NoSQL database designed for business critical applications, it is also known as Membase.It helps in delivering scalibility, unparalleled performance, financial value, and also unmatched versality at scale across hybrid deployments and cloud.
Couchbase runs on devices and manages synchronization to the server, and is used for providing low latency data management for IoT applications, mobiles and large scale web.It is designed for building interactive web applications and also helps in providing easy to scale key value ot JSON documents.


What is Couchbase server?

Couchbase Server is a NoSQL database which is faster, elastic, and easy to use, it is also regarded as the finest oriented database software packages.
Couchbase is also known as Membase, distributed, multi model NoSQL file database software package which is advanced for collective applications.


What is Apache CouchDB?

Apache CouchDB is an open source database which is developed by Apache Software Foundation and is implemented and written in Erlang, C++, JavaScript and C.It helps in allowing us in running a single logical database server on a number of VMs or servers.
The database helps in collecting and storing data in JSON Document formats, and can be achieved in a simplified way by using CouchDB across different computing devices because it makes use of schema-free data models.


What are the features of the Couchbase Server?

The basic features of the Couchbase Server are: FAST - it is quick and facilitates the lower latency and highest throughput, the performance cost is low and is remarkable sign.
SIMPLE - it is simple in managing, installing, getting expanding and in using it.
ELASTIC - it helps in distributing the data and I/O over the virtual machines.
RELIABLE - it is stable and enterprise ready software so that if anyone rely on mission critical application.


Name the elements which are present in Couchbase Node?

Index Service, Data Service, Cluster Manager component and Query Service are the elements of Couchbase Node.

How many functional blocks have involved in Couchbase Server

There are 2 types of blocks in Couchbase Server:
Data Manager - it is responsible in storing and extracting data from applications in answer to data processing requirements.
Cluster Manager - Helps in the arrangement plus the performance of all nodes in a couchbase sever clusters.


How can we find and fix a Rails and Couchbase memory leak?

We can add API in Couchbase by using the code below:

def loop_bucket_gets
    bucket = Couchbase::Bucket.new({:node_list => ['xxx.xxx.xxx.xxx:8091', 'yyy.yyy.yyy.yyy:8091'],
                                    :bucket => 'Foo',
                                    :pool => 'default',
                                    :expires_in => 1.day,
                                    :default_format => :marshal,
                                    :key_prefix => '_foo'
                                   })

    i = 0
    loop do
      begin
        i += 1
        bucket.get "ABC#{i}"
      rescue ::Couchbase::Error::Base => e
        nil
      end
    end
  end




How can we use HTTPS replication with iOS Couchbase Mobile?


[info] [<0.327.0>] Retrying HEAD request to https://user:password@mycompany.cloudant.com/mydb/ in 16.0 seconds due to error {'EXIT',
{no_ssl_server,
    {gen_server,call,
        [<0.347.0>,
         {send_req,
             {{url,
                  "https://user:password@mycompany.cloudant.com/mydb/",
                  "mycompany.cloudant.com",443,"mycompany","password",
                  "/mydb/",https,hostname},
              [{"Accept","application/json"},
               {"User-Agent","CouchDB/2.0.0-beta"}],
              head,<<>>,
              [{response_format,binary},
               {inactivity_timeout,30000},
               {is_ssl,true},
               {socket_options,[{keepalive,true},{nodelay,false}]},
               {ssl_options,[{depth,3},{verify,verify_none}]}],
              infinity}},
         infinity]}}}



What are the 4 subsystems which function on every node?

The four types of subsystem are:
  • Pulses - helps in regularly exchanging words with the presently designated cluster head in offering well being revises.
  • Progression Monitor - helps in carrying out the limited information executive and resuming unsuccessful procedures and contributing condition data to the pulsing piece.
  • Pattern Manager - helps in knowing every node in the cluster that has pattern.
  • Worldwide Singleton Supervisor - helps in selecting cluster head if the previously voted head and monitoring.

How to merge data in Couchbase with map reduce?

We can merge data by using the code given below:

function(doc, meta) {

  var getStep = function(stepName, exit, mapper) {
    if (meta.id.indexOf(stepName) !== -1) {
      var hotelId = parseInt(meta.id.replace(stepName + '_', ''));
      if (hotelId > 0) {
        var result = {
          hotelId: hotelId,
          exit: exit
        };
        if (mapper !== undefined) {
          mapper(result);
        }
        return result;
      }
    }
    return null;
  };

  var photos = getStep('PHOTOS', 7);
  if (photos != null) {
    emit(photos.hotelId, photos);
  }
  var pricing = getStep('PICR', 5);
  if (pricing != null) {
    emit(pricing.hotelId, pricing);
  }
  var owner = getStep('OWNER', 1);
  if (owner != null) {
    emit(owner.hotelId, owner);
  }
  var amenity = getStep('AM', 4);
  if (amenity != null) {
    emit(amenity.hotelId, amenity);
  }
  var description = getStep('HDESC', 3, function(result) {
    result.description = doc.description;
    result.hotelRoomTypeId = doc.hotelRoomTypeId;
    result.starRating = doc.starRating;
  });
  if (description != null) {
    emit(description.hotelId, description);
  }
  var contact = getStep('DC', 3, function(result) {
    result.email = doc.emailAddress;
    result.contact = doc.mainContactName;
  });
  if (contact != null) {
    emit(contact.hotelId, contact);
  }
  var location = getStep('LOC', 2, function(result) {
    result.city = doc.cityName;
    result.zip = doc.postalCode;
    result.country = doc.countryName;
    result.street = doc.stateName + ', ' + doc.streetName;
  });
  if (location != null) {
    emit(location.hotelId, location);
  }
  var property = getStep('PRP', 1, function(result) {
    result.paymentMethodId = doc.paymentMethodId
  });
  if (property != null) {
    emit(property.hotelId, property);
  }
}



What is a Bucket in Couchbase?

Couchbase Buckets are in storing data which can be flushed, created, deleted and edited, and also helps in storing the items in the buckets.It supports indexing, replication, data persisting, N1Ql queries, views and caching.
Bucket types in Couchbase are as follows:
Couchbase Buckets
Memcached Buckets
Ephemeral Buckets