Do domain extensions matter at early stage? Lets say if I buy domain with .in then will that look like saas application is India specific or something like that?

That is how its commonly considered. .in is a ccTLD (Country code Top Level Domain) - so it will be understood as a product / service of and for India.

I actually differ on this. I feel a lot of users will end up googling your product or clicking on links sent by others. Very rarely do we type in a domain name nowadays. So if you are getting a good name in another TLD - even if it is not a popular one, it should be ok. Some recent examples of notable companies doing so are: zoom.us and notion.so .coms are quite difficult to come by nowadays. .ins are also fine in my book. Yes it is India specific - but India does not add a restrictions on people to register it. Just remember that .in does not offer WhoIs privacy. .io domains actually are for the British Indian Ocean Territory - but you see many companies use it (they are quite expensive though). Also check out .co domains (they are rare as well nowadays)

The domain name adds to the overall brand image. So it is better to choose a clean relatable name and based on what audience you are targeting. If the audience is more of non-technical users, and you target a global audience. I would say go for .com. If it is technical you could opt .io, .co, .so etc.. If the target audience is within a country .in or .us or similar ccTLD would make sense. Rebranding later is a big and risky task. So it is better to choose your brand name and domain name wisely from start itself. Context: I have products with domain collect.chat, reach.at, whatsform.com

My plan is to make use of subdomain. For example landing page will be on myapp.com and then application will be on app.myapp.com so I want to separate out landing page and application. Is this good idea? Or should I keep landing page and app both same?

Best practice is to separate landingpage and application. By doing so, deployment of one will not affect other and you can easily use any platform of choice for both.

@kind-helicopter-52332 But should I deploy landing page and application on same server or different?

If your actual app and landing page don't share the same tech stack, then auto redirection is going to be a challenge or involve hacks. You could think about leaving a cookie which is readable by all sub-domains and on the basis of this cookie, your landing page can redirect to your sub-domain. However, what I would do is to keep your app on a sub-domain like: app.xyz.com and from there, you can control the behaviour that you desire. Your landing page would have a Login / Signup button which redirects to your sub-domain. That ways, your landing page can be on Wordpress or any other platform and I agree with Shyjal - that it is a simple trade-off. Most people don't mind clicking on a Login button to be logged in automatically. Again, these are indie hacker tips - once you have more resources or are willing to spend more time integrating both these on the same platform, you can definitely do it -- but it comes with rigidity and issues that you have already seen which needs time to iron out.

Yes got your point Saurabh. Also I have limited knowledge of nginx 😅