Elastic

• What is the Elastic Stack?
• Explain what is Elasticsearch
• What is Logstash?
• Explain what beats are
• What is Kibana?
• Describe what happens from the moment an app logged some information until it’s displayed to the user in a dashboard when the Elastic stack is used

Elasticsearch

• What is a data node?
• What is a master node?
• What is an ingest node?
• What is Coordinating node?
• How data is stored in elasticsearch?
• What is an Index?
• Explain Shards
• What is an Inverted Index?
• What is a Document?
• You check the health of your elasticsearch cluster and it’s red. What does it mean? What can cause the status to be yellow instead of green?
• True or False? Elasticsearch indexes all data in every field and each indexed field has the same data structure for unified and quick query – ability
• What reserved fields a document has?
• Explain Mapping
• What are the advantages of defining your own mapping? (or: when would you use your own mapping?)
• Explain Replicas
• Can you explain Term Frequency & Document Frequency?
• You check “Current Phase” under “Index lifecycle management” and you see it’s set to “hot”. What does it mean?
• What this command does? curl -X PUT “localhost:9200/customer/_doc/1?pretty” -H ‘Content-Type: application/json’ -d'{ “name”: “John Doe” }’
• What will happen if you run the previous command twice? What about running it 100 times?
• What is the Bulk API? What would you use it for?
• Query DSL
• Explain Elasticsearch query syntax (Booleans, Fields, Ranges)
• Explain what is Relevance Score
• Explain Query Context and Filter Context
• Describe how would an architecture of production environment with large amounts of data would be different from a small-scale environment

Logstash

• What are Logstash plugins? What plugins types are there?
  What is grok?
• How grok works?
• What grok patterns are you familiar with?
• What is _grokparsefailure?
• How do you test or debug grok patterns?
• What are Logstash Codecs? What codecs are there?

Kibana

• What can you find under “Discover” in Kibana?
• You see in Kibana, after clicking on Discover, “561 hits”. What does it mean?
• What can you find under “Visualize”?
• What visualization types are supported/included in Kibana?
• What visualization type would you use for statistical outliers
• Describe in detail how do you create a dashboard in Kibana

Filebeat

• What is Filebeat?
• If one is using ELK, is it a must to also use filebeat? In what scenarios it’s useful to use filebeat?-
• What is a harvester?
• True or False? a single harvester harvest multiple files, according to the limits set in filebeat.yml
• What are filebeat modules?

Elastic Stack

• How do you secure an Elastic Stack?

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

I publish technical articles at DevOps School, travel stories at Holiday Landmark, stock market insights at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow, and SEO and digital marketing strategies at Wizbrand.