Database / Supabase Intermediate to Advanced Interview Questions

How does Supabase expose custom Postgres functions as callable RPC endpoints?

Any function defined in your Postgres schema is automatically exposed by PostgREST at /rest/v1/rpc/<function_name>, callable via POST with the function's arguments as a JSON body — no separate route registration is required.

create function calculate_discount(price numeric, percent numeric)
returns numeric as $$
  select price - (price * percent / 100);
$$ language sql;

From the client, this becomes supabase.rpc('calculate_discount', { price: 100, percent: 10 }). RPC is the natural escape hatch when a query needs logic that a plain table filter can't express — conditional aggregation, multi-step calculations, or anything that should run as one atomic unit inside Postgres rather than round-tripping data to the client and back.

Take quiz

Where does an RPC-callable Postgres function get exposed by PostgREST? /rest/v1/rpc/

✓ Correct! Well done.

It isn't exposed automatically

✗ Try again, that's not it.

/storage/v1/functions

✗ Try again, that's not it.

/auth/v1/rpc

✗ Try again, that's not it.

Why reach for an RPC function instead of a plain table query? To upload a file to Storage

✗ Try again, that's not it.

When logic needs multi-step calculation as one atomic Postgres operation

✓ Correct! Well done.

To change a user's password

✗ Try again, that's not it.

To subscribe to Realtime events

✗ Try again, that's not it.

More Related questions...

How does Supabase expose custom Postgres functions as callable RPC endpoints? What is the difference between a SECURITY DEFINER and a SECURITY INVOKER Postgres function? How does pg_cron enable scheduled jobs directly inside a Supabase Postgres database? What is the difference between a read replica and the primary database in a Supabase project? When should you use a read replica versus scaling the primary database's resources? What is the difference between daily backups and Point-in-Time Recovery in Supabase? How does Supabase's database branching feature isolate schema changes per git branch? When would you choose a preview branch over testing migrations directly in staging? What is the difference between a custom access token hook and a raw JWT claim? Why should you avoid embedding sensitive business data directly inside JWT claims? How does Supabase support anonymous sign-ins, and how do you convert one to a permanent account? What is the difference between linking an OAuth identity and creating a brand-new user account? How is Storage object access controlled compared to table-level Row Level Security? What is the difference between resumable (TUS) uploads and standard uploads in Supabase Storage? How does Supabase's image transformation feature resize images without a separate CDN service? What is the difference between LISTEN/NOTIFY and Supabase Realtime's Postgres Changes channel? What is the difference between schema-per-tenant and RLS-based multi-tenancy? Why is EXPLAIN ANALYZE useful before optimizing a slow Supabase query? What is the difference between JSONB and a fully normalized relational schema in Postgres? When should you use a JSONB column instead of creating additional relational tables? How does wrapping auth.uid() in a subquery improve Row Level Security performance? Why do we use SECURITY DEFINER functions when RLS would otherwise block a needed operation? How does pg_net let Postgres make asynchronous HTTP calls without blocking a transaction? Explain the lifecycle of a Point-in-Time Recovery (PITR) backup in Supabase? How does a custom access token Auth Hook let you enrich a user's JWT with custom claims? How does Supabase enforce multi-factor authentication (MFA) at the session level? Why doesn't disabling RLS on a table make it invisible in the auto-generated API docs? Explain the internal working of Supabase Vault for storing encrypted secrets in Postgres? Why should you store third-party API keys in Vault instead of a plain table column? When should you choose LISTEN/NOTIFY over Supabase Realtime for internal service communication? How can you optimize a multi-tenant schema design using Row Level Security instead of schema-per-tenant? How do you troubleshoot a Postgres query that performs well in the SQL editor but slowly through the REST API? Explain the execution flow of a private Realtime broadcast channel authorized by Row Level Security? Why do private Realtime channels need their own RLS-style authorization check? How does Supabase's connection string differ between the direct connection, session pooler, and transaction pooler? Why doesn't the transaction pooler support prepared statements the way a direct connection does? How can you optimize zero-downtime schema migrations for a table already receiving production traffic? What happens when a long-running migration locks a table that's still receiving live writes? How does Supabase Studio's SQL editor differ from running migrations through the CLI in a CI pipeline? Which is better for production schema changes, editing directly in Studio or CLI-managed migrations, and why?

Show more question and Answers...

Apache Cassandra Intermediate and Advanced interview questions

Comments & Discussions

MongoDB Interview questions 31 SQL 39 REDIS 69 Apache Cassandra Interview Questions 27 Amazon DynamoDB Interview questions 6 InfluxDb interview questions 30 InfluxDb interview questions II 50 Vector database interview questions 45 PineCone Database Interview questions 50 PineCone Database Interview questions II 5 Snowflake Interview Questions 45 CouchDB Interview Questions 45 Liquibase interview questions 34 Azure Cosmos DB interview questions 34 ChromaDB Interview Questions 38 pgvector basics Interview Questions 40 Supabase basics Interview Questions 30 Supabase Intermediate to Advanced Interview Questions 40 Apache Cassandra Intermediate and Advanced interview questions 45 RocksDB Basics Interview Questions 47 Mnesia basics Interview questions 48 Mnesia intermediate to advanced Interview questions 48 SQLite Interview questions 48 Google Spanner Database Interview questions 50 ScyllaDB Interview questions 50 Qdrant Vector DB Interview questions 50 Weaviate Vector database Interview questions 50 Milvus Vector database Interview questions 50 DuckDB Interview questions 50

Recently added questions

How do you configure access logging in Caddy? What are Caddy modules? How do you install Caddy on Ubuntu Linux? What is the encode directive used for? What is the purpose of the header directive? List the certificate authorities Caddy can obtain TLS certificates from? What is automatic HTTPS in Caddy? What are the types of Caddy configuration formats? How do you serve static files with Caddy? What is the purpose of the file_server directive? What is the respond directive used for? Define matchers in Caddyfile? How do you redirect HTTP to HTTPS in Caddy? What is the Caddy admin API? What is Caddy Server? What are the key features of Caddy? What is a Caddyfile? What is the purpose of the reverse_proxy directive? How do you start, stop, and reload the Caddy service? How do you use environment variable placeholders in a Caddyfile?

	Interviews Questions Java Spring Hibernate DevOps Testing API BigData Web Erlang AI Database Integration Cloud Python Scala Tools Golang SAP	About Javapedia.net Javapedia.net is for Java and J2EE developers, technologist and college students who prepare of interview. Also this site includes many practical examples. This site is developed using J2EE technologies by Steve Antony, a senior Developer/lead at one of the logistics based company. Follow Javapedia updates
	contact: javatutorials2016[at]gmail[dot]com
Kindly consider donating for maintaining this website. Thanks.
	Copyright © 2026, javapedia.net, all rights reserved. Privacy Policy · Terms of Service.