SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a1c8cfc92c64833be4ba55131a4f74f0a84a39e691d80e96f0d29734298aef38' 
  AND token = '+tZ+ud4Tovw0KxWKlCa9WHZGvPxVhJKgLMMlqXg0ryw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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