SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df54c82ba12061eab71e12f8818bb9e0eae09c9475172c65dbc5c876f719d463' 
  AND token = 'StmDMJq7SiJLPDflGOzX6pkG53MBH9xqQYRpweyft1c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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