As a software developer, how can I ensure I remain employable after age 50?

I used to think the same way.  I've been programming UNIX/Linux for around 30 years.  I liked writing code.  I wanted my job to be writing code, and I wanted some company to pay me to do that.

I absolutely LOVE writing code now - because I only write WHAT I want to write, WHEN I want to, and HOW I want to.  (I.e. it's no longer part of my job.  I write code as a hobby now.) 

I absolutely LOVE my job now - it's WAY better than any job I've ever had before - including when I was a consultant, and including when I worked for myself (I was CTO of my own startup some years ago).

My day job is: HELP PEOPLE.  I found a very good fit in customer service.  

I'm now a top shelf systems administrator, and I leverage my coding skills to solve problems that would make many sysadmins heads spin. For example, I was asked to action a db import the other day.  Mid-import, the load on the server went almost to zero, and memory usage started to climb. 

The import had dead-locked with the customer's runtime application logic.  

Because of how apache works, and because most customers over-commit apache in terms of how they set MaxClients (they allow Apache's worst-case memory footprint to be larger than their total available memory)... in this sort of a case, it's imperative to act QUICKLY to correct the situation, or the server will very probably crash.

Most sysadmins in that case would immediately stop apache, which I did.  They would then abort the import, probably restart mysql to clear the deadlock, and restart the import.  That, I did not do - it's overkill.

Instead, I stopped apache, ran "mysqladmin processlist > queries", edited the file "queries" in vim and... 

-> deleted the header, the footer and the specific db import query I did NOT want to kill, 

-> issued :1,$s/^|/kill /

-> issued :1,$s/|.*/;/ 

-> wrote the file and exited.  

That gave me a file full of lines like this: 

kill 12345 ; 

kill 67890 ;  

...then I ran "mysql

It was a 4.5G import, so that was a good thing; restarting it would have added hours to the downtime.  

This isn't something your typical dev knows how to do correctly.  It's not something your typical admin knows how to do correctly.  And it's not even something your typical DBA knows how to do correctly.  It's something I knew how to do correctly, leveraging my years of experience.  

I'm sharing this because it shows there's still a need for people who can solve difficult computing problems, accurately and quickly, but outside of the programming domain.  Your experience level may well make you IDEAL for this sort of position, so if you find it at all compelling, I recommend that you:

• review all of your past positions to see how each and every one of them had "customer service" as some aspect of what they were about
• rework your resume to exude that aspect of what you did
• apply for an entry-level position in customer service at a hosting company