DNS A Record Troubleshooting & TTL

So, www. example. com is our domain and the A record simply means we'll map the exact IP address, the exact IPv4 address, which is mapped to this particular domain. Okay? And what is TTL? TTL is simply time to live. So, how long this going to stay in this table? And 3600 means it is for 1 hour. So, it is 3600 seconds. Simply, if you face any issue while migration of, for example, your database server or your application server, it could be that your A record is still pointing to the old IP address. You have not updated your A record or maybe your TTL has not yet expired. So, it might be a possibility that for the next 1 hour or 2 hours, the record is still active. While users are trying to hit the domain and it should route to the new IP address, it is still pointing to the old one. So, you have to also think on those lines when someone throws a scenario-based question to you, you have to think about, "Okay, which particular record might be into play in this particular scenario? " And a good practice is whenever you are doing any such migration, you lower this TTL value to maybe 60 seconds or maybe few minutes rather than hours, so that you can do your testing.