SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f849d5fdfd922c751ea2aa7f2931466700f24dcd0dff39289b9409f1d771af4' 
  AND token = 'b91txvTu1GURhf9TtHYUSOdef9AEDXhVPL6NwxRcY00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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