SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '687e627f626cc2fe653cd2ecf72a64eca6a6028ed86fcfb8f4ad649ac145ff4f' 
  AND token = 'dXiUC+kK2jyXhiGLkTWwGLOUmYVCjCw8g80q720GaEM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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