SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc1267b9f1cd9d37feaabe576c8e78eddcd7f37e55e812242c0e25518972d6fc' 
  AND token = 'EL9GkC/q1ryGMP8aRhZHDE+ZafqAuh39hGAKcQy2Cm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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