Best setup report builder within SaaS?

Hi everyone,

We've built a CRM and are looking to implement a report builder in our app.

We are exploring the best solutions for our needs and it seems like we have two paths we could take:

• Option A: Build the front-end/query builder ourselves and hit read-only replica
• Option B: Build the front-end/query builder ourselves and hit a data warehouse we've built using a key-base replication mechanism on BigQuery/Snowflake, etc..
• Option C: Use third party tools like Explo etc...

About the app:

• Our stack is React, Rails, Postgres.
• Our most used table (contacts) have 20,000,000 rows
• Some of our users have custom fields

We're trying to build something scalable but most importantly not spend months in this project.
As a result, I'm wondering about the viability of Option A vs. Option B.

One important point is how to manage custom fields that our users created on some objects.

We were thinking about, for contacts for example, we were thinking about simply running with joins across the following tables

• contacts
• contacts_custom_fields
• companies (and any other related 1:1 table so we can query fields from related 1:1 objects)
• contacts_calculated_fields (materialized view to compute values from 1:many relationship like # of deals the contacts is on)

So the two questions are:

• Would managing all this on the read-only be viable for our volume and a good starting point or will we hit the performance limits soon given our volume?
• Is managing custom fields this way the right way?