This probably matters much less than you think.

There's no standard or widely-used set of titles for tech jobs. A person may be called SWE III at one place and Senior Programmer at another. I think it's best to show the title and explain it if that seems necessary -- assume people reading the CV don't know what SWE III or PA-2 means. Explaining unclear or unusual titles also gives you a chance to get more searchable keywords into the CV -- just write "programmer" or "software developer" after the title.

If you did military service your title(s) almost certainly won't make sense to civilians, so you will have to translate them.

A company I worked for let me use XCommander as my title. Another had titles like "Deus ex Machina" and "Kernel Ninja." I wouldn't advertise a goofy title like that on a CV, I would translate it to something that better described the actual position.

In any case titles are not something people reading your CV are going to care a lot about because everyone with any experience in the industry already knows titles are mainly BS. When you've seen hundreds of people with two years experience calling themselves Senior Software Engineers and Chief Technology Officer (of their own company) on their CVs you figure out pretty fast to look past the wrapping paper.

Remember that a CV/résumé has one purpose: to get an interview. Never lie, but be sure to highlight and focus on the skills and experience the prospective employer wants to see. No one cares about your titles or objectives or personal desires, and no one needs to read an explanation for an inscrutable joke or jargon title. Make it clear, remember you have a few seconds to get on the short list or in the bin.

Some companies have rediculous titles though. I've worked at a school district, the job was being an IT lackey (configure cisco switches, install said switches at schools, prep and install computers for instructors, front office, computer labs, debug all of those, basic computer instructions for adult users, etc), but the job title was something something classroom helper (not instructional aide, but similar) because it was too much bueracracy to get a new position classified into the system, so they took one close enough and called it a day. If I put that title on my resume, it would be most unhelpful for everyone.

When I worked at Yahoo!, my title was Technical Yahoo!, then Technical Yahoo!, Senior... etc. That's fine if an ex-y! is reviewing my resume (and there are a lot of those), but for other people it would be helpful if I wrote (Backend) Software Engineer.

I've seen people do this egregiously - the last startup I worked at people almost seemed to just make stuff up on LinkedIn for their title, that knowing their official title and actual responsibilities was BS (although some people had real internal titles that also didnt really mean what they said in the real world.) A lot of "lead" implying "the lead", when it really meant "senior" as in there are many, it means you have 2 years work experience and no reports. And a lot of "head of" when what was headed was 2 people, but framed as a region or service line.

I have subtly played with my title occasionally, to try and reconcile it with normal industry titles. But I've found it doesn't change anything, and have reverted to just putting my employer given titles and explaining them, as the other comment said

It all depends. At current company we have flat structure, no titles like "Senior Developer", "Junior Developer" but clearly there is a difference between new people and people that have years of experience.

Issues can also be if you are working for some institutions that have rigid naming scheme, e.g. all of the IT people have in their contracts "IT specialist of 2nd grade". Take a look at this job add https://epso.europa.eu/job-opportunities/temporary/9593-eppo... - "IT Officer – Systems, Network, Database and Security. Grade: FG IV".

No, because I felt that some of these titles seemed quite ambiguous despite showing progression. I spent several years at the company and worked in several different areas. I felt that using titles like "Build Engineer" or "Tools Engineer" was more useful than "Software Engineer I", "II", or "III" even though they were my "official" titles. I've thought about changing it a few times to display seniority progression, but it's not felt quite as intuitive as what I have now.

My job title was Assistant Manager while the actual role was that of a Senior Business analyst. Similarly, in another organisation, the title was 'Senior Software engineer'. I was neither senior nor a software engineer but a Data Scientist.

I had to change the title on the resume/job portals. If not, the resume would not get shortlisted for any job opportunities.

Sure within reason. Don’t give yourself a title you can’t back up but more descriptive is fine.