SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81639de8a92c1160061b9526a64c0395afbb040d2574e0dc3825267c22ac7172' 
  AND token = 'QiRbqIKPKqRreod+UhYcfMaGsp9cTNYUQHNFJIGYQsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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