SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ff1fca7b6e1573ad7b8b68d96986b697549da134d52c19017f1b264a69efa14' 
  AND token = 'JWDT0m93CrvgLfArMOs+BjXNY/tnUwOkBUb/ulxQsIY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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