SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '748a4b3b625263e917eada500f2bf0bf9836364603ed8cee11dc29a577de79f6' 
  AND token = '4qWwV3Z4O+IvvRXq+4CK72DI6fMcBdcWINPjOSSz5Vo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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