Table as an Index?

PostgreSQL 11

Requirements:

• Uniqueness must be guaranteed (not duplicated)
• MUST not lose any data.

The data I get is NOT uniquely identified, so I am left with semantic comparison of the values to determine uniqueness.

E.g.

CREATE TABLE data.stuff
(
  recorded  BIGINT   NOT NULL,
  source_id INT      NOT NULL,
  key       TEXT     NOT NULL,
  value     TEXT     NOT NULL
  
  PRIMARY KEY (recorded, source_id, key, value)
);

INSERT INTO data.stuff (recorded, source_id, key, value)
VALUES (?, ?, ?, ?)
ON CONFLICT (recorded, source_id, key, value)
DO NOTHING;

It seems like my SQL is just saying that I want an index for a table which feels silly…
Is there a better way to do this?