SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '500480444434761c02cd59e24e4cdeebc4944ab71d603f58ac8404e627d6d380' 
  AND token = '0iFuZOvBNI1WGsZJbzCU+emW1HYTfupkTEs/w0xZYKY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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