Context

Teams often need to centralize repeated database logic such as validations, updates, and batch operations. Stored procedures are one way to keep that logic close to the data.

Question

Explain what stored procedures are in PostgreSQL and when you would use them. In your answer, cover:

1. What a stored procedure is and how it differs from a regular SQL query or function
2. Typical use cases where stored procedures are a good fit
3. Benefits and drawbacks of using them
4. Situations where application-layer logic may be a better choice

Scope Guidance

Keep the answer practical and interview-focused. The interviewer expects a clear definition, a few realistic examples, and a balanced discussion of when stored procedures improve maintainability, security, or performance versus when they add complexity.

Definition of a Stored Procedure

A stored procedure is a named database program stored in PostgreSQL and executed with the CALL statement. It can contain multiple SQL statements and procedural logic, making it useful for encapsulating repeatable database operations.

CREATE PROCEDURE close_order(p_order_id INT)
LANGUAGE plpgsql
AS $$
BEGIN
  UPDATE orders
  SET status = 'closed'
  WHERE order_id = p_order_id;
END;
$$;

Procedure vs Function

In PostgreSQL, functions are typically used to return a value or a result set and can be called inside SQL expressions. Procedures are invoked with CALL and are better suited for operational workflows, especially when you want to execute a sequence of statements as a unit.

CALL close_order(101);

Centralized Business Logic

Stored procedures help centralize logic that would otherwise be duplicated across multiple applications or services. This can reduce inconsistency when many clients need to apply the same validation or update rules.

Security and Controlled Access

A procedure can provide a controlled interface to underlying tables so users do not need direct write access. This is useful when you want to restrict how data is inserted or updated while still allowing approved operations.

GRANT EXECUTE ON PROCEDURE close_order(INT) TO app_user;

Trade-offs and Maintainability

Stored procedures can improve consistency and reduce network round trips, but they can also make versioning, testing, and debugging harder if overused. They are best used for well-defined database-centric workflows rather than all application logic.