ElasticSearch vs Relational Database

Question

I'm creating a microservice to handle the contacts that are created in the software. I'll need to create contacts and also search if a contact exists based on some information (name, last name, email, phone number). The idea is the following: A customer calls, if it doesn't exist we create the contact asking all his personal information. The second time he calls, we will search coincidences by name, last name, email, to detect that the contact already exists in our DB. What I thought is to use a MongoDB as primary storage and use ElasticSearch to perform the query, but I don't know if there is really a big difference between this and querying in a common relational database.

EDIT: Imagine a call center that is getting calls all the time from mostly different people, and we want to search fast (by name, email, last name) if that person it's in our DB, wouldn't ElasticSearch be good for this?

Answer 1

A relational database can store data and also index it.

A search engine can index data but also store it.

Relational databases are better in read-what-was-just-written performance. Search engines are better at really quick search with additional tricks like all kinds of normalization: lowercase, ä->a or ae, prefix matches, ngram matches (if indexed respectively). Whether its 1 million or 10 million entries in the store is not the big deal nowadays, but what is your query load? Well, there are only this many service center workers, so your query load is likely far less than 1qps. No problem for a relational DB at all. The search engine would start to make sense if you want some normalization, as described above, or you start indexing free text comments, descriptions of customers.