SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76da35ae031210861efea273496cbebc98e6e9fa776b85f44ec4035e9dc24538' 
  AND token = 'JHJnmt89qM8GZ0dXTB+Xq6FGX8eBiqaFIHF0k+IyIt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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