SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '251dbf45ee361fd0642f6fee8041ad5d81e9215a5728c789201f626899d031e8' 
  AND token = 'wMuhqhAjuYl3eZVjmZJ0UffAFibQbimyCgK1DhicZY4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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