Elasticsearch takes long time to update simple index

I have installed ES and Logstash 7.2.0 in 2 servers and I tried pushing a simple text file from Logstash to ES. The Logstash seems to send the data quickly, however, the ES takes about 5 mins (everytime) to update this data in its index.

ES yml:

cluster.name: myes
node.name: elk04
bootstrap.memory_lock: true
http.port: 9200
cluster.initial_master_nodes: ["elk04"]

Logstash conf:

input {
        file {
        path => "/etc/logstash/conf.d/mytest.txt"
        start_position => "beginning"
        sincedb_path => "/dev/null"
        output {
           elasticsearch {
               hosts => ["<esIP>:9200"]
               index => "text"
               doc_as_upsert =>true}
               stdout { codec => rubydebug }

the contents of the text file is just 4 lines for testing:

this is a test text
for logstash updation
adding another line
this is to check updates

Please help me out with this.