Sorry for going offtopic

"How do you make sure that a celebrity's tweet reaches all of her followers in less than 3 seconds?"

Looks like the interviewer has atleast read the first chapter of "Designing Data-Intensive Applications: The Big Ideas Behind Reliable, Scalable, and Maintainable Systems"

If you read and understand the above book, I am reasonably sure that you can crack most of the system design interviews.

So, I thought I'd type up a bit of more detailed explanation of my story and why I think real estate is a great investment for software developers, since my previous comment was a little lacked.

I bought my first house when I was 19.

It's a little two bedroom shack in Boise, Idaho, which I bought in 1999 for $68,000.

I still have that little shack. Today it's worth about $135,000 and the tenants I had in it essentially paid the mortgage on it and I own it free and clear.

I've actually got 26 total rental units and I generate about $10k a month of almost completely passive income off of them, net.

I made a ton of mistakes along the way, but I learned quite a bit--which I'm happy to share.

Over the years, I tried to buy one property every year.

At first I could only afford small properties and would put 10% down, so I was a bit leveraged.

But, eventually I was able to afford bigger properties and put more money down.

I always bought properties using 30 fixed loans and that ended up working out well.

I watched in horror as many of the other investors I knew--who were really speculators--went under, during the big housing crash.

I actually thrived during this time, picking up properties for cheap.

All the time I was working as a software developer, I had this goal of retiring early.

I kept saving as much as I could and investing real estate... little by little.

Like I said, I made mistakes, but learned from them and got smarter as I got more experienced.

Eventually, I had built up enough cash flow to actually "retire." This happened a few years ago.

Why is real estate such a good investment?

Well, I think there are two main factors: leverage and hedging against inflation.

Leverage is extremely powerful.

A bank will lend you a large amount of money, sometimes 90% or more, for you to invest--if you buy real estate.

This isn't the case with other investments.

So, you can buy a house for $100k, put $10k of your own money into it and if it goes up 10%, and is worth $110k, you make 100% return on your $10k.

That's insane. I don't know other investments where that is possible with such low risk--if you mitigate the risk properly.

Now, I don't depend on appreciation--and you can't count on it--but, you don't even need it.

Just the cash flow alone can get you excellent returns on your money. Again, with little risk and huge upsides.

Hedging against inflation is also a beautiful part of real estate investment.

Most other investments are hurt by inflation, real estate isn't.

In fact, if you owe money on a mortgage and inflation hits, you actually owe less.

Home values go up with inflation, as do rents.

I know it's a bit difficult to believe--I probably wouldn't if I hadn't done it myself--but, I have done it and I did escape the rat race.

Anyway, if you'd like to know more, let me know and I'll post the link to my YouTube videos and the video course (that is in beta) that I am releasing on specifically real estate investment for software developers.