SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a97599344ddd49a20d578ebd4ab47dcdf668303efd4cbdd474c8e3ee5f9fcb42' 
  AND token = 'qrwkocPXqVvNspE1fxYcyLXCcgM5isWMToHiBc9ErPk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}