Engineer goes off and creates the initial plan & sends it around. At a high level,it looks like this:

    Client side code

        Set up

            snippet lets users know there is a new options in preferences

            if the app language pref  does not map to a supported language, the pref panel is greyed out with a message that their language is not supported by the EU service

            if it does, user clicks ToS, privacy policy checkbox, confirms language

            app contacts server

            if server not available, throw up offline error

            if server available, upload device id, language, url list

            notify user setup is complete

            enable  upload service

        When new tab is opened or refreshed

            using device id, send a sql query for matching row of url+device id


Server side code

    Set up

        poked by client, adds rows to table, one for each url (tab)

    Periodic background translation job:

        finds urls of rows where the translated blob is missing

        for each url, submits untranslated blob to EU’s service

        sticks the resulting translated text blob back into the table

    Periodic background deletion job:

        finds rows older than 2 days and evicts them

        unless that is the last row for a given device id, in which case hold for 90 days

    Database layout

        table columns: device id, url, timestamp, language, untranslated text, translated text


 The 3rd Meeting:

Engineer: Did y’all have a chance to look over the plan I sent out? I haven’t received any email feedback yet.

DBA: I have a lot of concerns about the database table design. The double text blobs are going to take up a lot of space and make the server very slow for everyone.

Operations Engineer: ..and the device id really should not be in the main table. It should be in a separate database.

Engineer: why? That’s needless complexity!

Operations Engineer: Because it should be stored in a more secure part of the data center. Different parts of the data center have different physical & software security characteristics.

Engineer: “ oh”

Engineering Manager: You should design your interactions with the server to encapsulate where the data comes from inside the server. Just query the server for what you want and let it handle finding it. Building the assumption that it all comes from one table into your code is bad practice.

Engineer: ok

DBA: The double blobs of text is still a problem.

Engineer: Ok, well, let’s get rid of the untranslated text blob. I’ll take the url and load the page and acquire the text right before submitting it to the EU service. How does that sound?

Engineering Manager: I like that better. Also allows you to get newest content. Web pages do update.

Privacy Rep: I was wondering what your plans are for encryption? I didn’t see anything in your draft after it either way.

Engineer: If it’s on our server and we’re going to transmit it to an outside service anyway, why would we need encryption?

Privacy Officer: We’ll still have a slew of device ids stored. At the very least we’ll need to encrypt those. Risk mitigation.

Engineer: But they’re our servers!

Operations Engineer: Until someone else breaks in. We’ve agreed that the device ids will go in a separate secure table, so it makes sense to encrypt them.

Engineer: fine.

Privacy Officer: The good news is that if you design the url/text table well, I don’t think we’ll need to encrypt that.

Engineer: That’s your idea of good news?

Engineering Manager: Privacy Officer is here to help. We’re all here to help.

Engineer: Right, Sorry Privacy Officer.

Privacy Rep: It’s ok. Doing things right is often harder.

Privacy Officer: Anyway, I wanted to let you all know that I’ve started talking with Legal about the terms of service and privacy policy. They promise to get to it in detail next month. So, as long as we stay on the stage servers, it won’t block us.

Engineering Manager: thanks. Do you have any idea how long it might take them once they start?

Privacy Officer: Usually a couple weeks. Legal is very, very through. I think it’s a job requirement in that department.

Engineer: Fair enough.

Operations Engineer: Speaking of legal & privacy, do you/they care about the server logs?

Privacy Officer: I don’t think so. The device id is the most sensitive bit of information we’re handling here and that shouldn’t appear in the logs right? I’ll still talk it over with the other privacy folks in case there’s a timestamp to ip address identification problem.

Operations Engineer: That’s correct.

Engineering Manager: Always good to double check.

Privacy Officer: By the way, what happens to a user’s data when they turn the feature off?

Engineer: … I don’t know. Product Manager didn’t bring it up. I don’t have a mock from him about what should happen there.

Privacy Officer: we should probably figure that out.

Engineer: yeah

Engineering Manager: I look forward to seeing the next draft. I think after you’ve applied the changes & feedback here you should send it out to the public engineering feature list and get some broader feedback.

Engineer: will do. Thanks everyone

Who brought up user data safety & privacy concerns in this conversation?

DBA, Engineering Manager, Privacy Rep.

The day after the first meeting…

Engineering Manager: Welcome DBA, Operations Engineer, and Privacy Officer. Did you all get a chance to look over the project wiki? What do you think?

Operations Engineer: I did.

DBA: Yup, and I have some questions.

Privacy Officer: Sounds really cool, as long as we’re careful.

Engineer: We’re always careful!

DBA: There are a lot of pages on the web, Keeping that much data is going to be expensive. I didn’t see anything on the wiki about evicting entries and for a table that big, we’ll need to do that regularly.

Privacy Officer: Also, when will we delete the device ids? Those are like a fingerprint for someone’s phone, so keeping them around longer than absolutely necessary increases risk for the user & the company’s risk.

Operations Engineer: The less we keep around, the less it costs to maintain.

Engineer: We know that most mobile users have only 1-3 pages open at any given time and we estimate no more than 50,000 users will be eligible for the service.

DBA: Well that does suggest a manageable load, but that doesn’t answer my question.

Engineer: Want to say if a page hasn’t been accessed in 48 hours we evict it from the server? And we can tune that knob as necessary?

Operations Engineer: As long as I can tune it in prod if something goes haywire.

Privacy Officer:: And device ids?

Engineer: Apply the same rule to them?

Engineering Manager: 48 hours would be too short. Not everyone uses their mobile browser every day. I’d be more comfortable with 90 days to start.

DBA: I imagine you’d want secure destruction for the ids.

Privacy Officer:: You got it!

DBA: what about the backup tapes? We back up the dbs regularly?

Privacy Officer:: are the backups online?

DBA: No, like I said, they’re on tape. Someone has to physically run ‘em through a machine. You’d need physical access to the backup storage facility.

Privacy Officer:: Then it’s probably fine if we don’t delete from the tapes.

Operations Engineer: What is the current timeline?

Engineer: End of the quarter, 8 weeks or so.

Operations Engineer: We’re under water right now, so it might be tight getting the hardware in & set up. New hardware orders usually take 6 weeks to arrive. I can’t promise the hardware will be ready in time.

Engineering Manager: We understand, please do your best and if we have to, Product Manager won’t be happy, but we’ll delay the feature if we need to.

Privacy Officer:: Who’s going to be responsible for the data on the stage & production servers?

Engineering Manager: Product Manager has final say.

DBA: thanks. good to know!

Engineer: I’ll draw up a plan  and send it around for feedback tomorrow.


Who brought up user data safety & privacy concerns in this conversation?

Privacy Officer is obvious. The DBA & Operations Engineer also raised privacy concerns.

The 1st Meeting

Product Manager: People, this could be a game changer! Think of the paid content we could open up to non-english speakers in those markets. How fast can we get it into trunk?

Engineer: First we have to figure out what *it* is.

Product Manager: I want users to be able to click a button in the main dropdown menu and translate all their text.

Engineering Manager: Shouldn’t we verify with the user which language they want? Many in the EU speak multiple languages. Also do we want translation per page?

Product Manager:  Worry about translation per page later. Yeah, verify with user is fine as long as we only do it once.

Engineering Manager: It doesn’t quite work like that. If you want translation per page later, we’ll need to architect this so it can support that in the future.

Product Manager: …Fine

Engineer: What about pages that fail translation? What would we display in that case?

Product Manager: Throw an error bar at the top and show the original page. That’ll cover languages the service can’t handle too. Use the standard error template from UX.

Engineering Manager: What device actually does the translation? The phone?

Product Manager: No, make the server do it, bandwidth on phones is precious and spotty. When they start up the phone next, it should download the content already translated to our app.

Engineer: Ok, well if there’s a server involved, we need to talk to the Ops folks.

Engineering Manager: and the DBAs. We’ll also need to find who is the expert on user data handling. We could be handling a lot of that before this is out.

Project Manager: Next UI release is in 6 weeks. I’ll see about scheduling some time with Ops and the database team.

Product Manager: Can you guys pull it off?

Engineer: Depends on the server folks’ schedule.

Who brought up user data safety & privacy concerns in this conversation?

The Engineering Manager.


In January, I laid out information in a presentation & blog post information for a discussion about applying Mozilla’s privacy principles in practice to engineering.  Several fellow engineers wanted to see it applied in a concrete example, complaining that the material presented was too abstract to be actionable. This  is a fictional series of conversations around the concrete development of a fictional mobile app feature. Designing and building software is a process of evolving and refining ideas, and this example is designed for engineers to understand actionable privacy and data safety concerns can and should be a part of the development process.


The example is fictional. Any resemblance to any real or imagined feature, product, service, or person is purely accidental. Some technical statements to flesh out the fictional dialogues. They are assumed to only apply to this fictional feature of a fictional mobile application. The architecture might not be production-quality. Don’t get too hung up on it, it’s a fictional teaching example.

Thank You!

    Before I begin, a big thank you to Stacy Martin, Alina Hua, Dietrich Ayala, Matt Brubeck, Mark Finkle, Joe Stevenson, and Sheeri Cabral for their input on this series of posts.

The Cast of Characters

so fictional they don’t even get real names

  1. Engineer
  2. Engineering Manager
  3. Service Operations Engineer
  4. Database Administrator (DBA)
  5. Project Manager
  6. Product Manager
  7. Privacy Officer, Legal’s Privacy Auditor, Privacy & Security there are many names & different positions here
  8. UX Designer

Fictional Problem Setup

Imagine that the EU provides a free service to all residents that will translate English text to one of the EU’s supported languages. The service requires the target language and the device Id. It is however, rather slow.

For the purposes of this fictional example, the device id is a hard coded number on each computer, tablet, or phone. It is globally unique and unchangeable, and so highly identifiable.

A mobile application team wants to use this service to offer translation in page (a much desired feature non-English speakers) to EU residents using their mobile app.  For non-english readers, the ability to read the app’s content in their own language is a highly desired feature.

After some prototyping & investigation, they determine that the very slow speed of the translation service adversely affects usability. They’d still like to use it, so they decide to evolve the feature. They’d also like to translate open content while the device is offline so the translated content comes up quicker when the user reopens the app.

Every New Feature Starts Somewhere

Engineer sees announcement in tech press about the EU’s new service and its noble goal of overcoming language barriers on the web for its citizens. She sends an email to her team’s public mailing list “wouldn’t it be cool apply this to our content for users instead of them having to copy/paste blocks of text into an edit box? We have access to those values on the phone already”

Engineering Team, Engineering Manager & Product Manager on the thread are enthusiastic about the idea.  Engineering Manager assigns Engineer to make it happen.


She schedules the initial meeting to figure out what the heck that actually means and nail down a specification.

Books reviews are entirely my opinion and I am not editor. Please take them with a pound of salt. If you are looking for an in depth review, this is not it.


‘American Lion’ focuses on President Andrew Jackson’s years in the White House, though it does cover his life start to finish. I became interested in the book after the author’s lively interview on the Daily Show. Then I forgot about it until I saw it lying on a friend’s shelf. He graciously lent me the book.

On Content:

The most fascinating part of the book dealt with the South Carolina Nullification crisis during Jackson’s time in office. The crisis was adverted, but the legal standing of a state’s right to nullify federal laws was not resolved. The Nullification crisis & its roots laid much of the legal groundwork for the American Civil War.  The South made many arguments about the ‘intents of the Framers’, to support their position, much like modern American politicians do today.

Monroe, a Founding Father (a Framer, former President, author of the ‘Virginia Resolutions’ cited in legal support of Nullification)  was alive and vocal that the ‘Virgina Resolutions’ did not extend to nullification and nullification of federal laws was not intended by the Constitution. He was roundly ignored by the South.

I found I learned more about the politics swirling about in the early days of America than about Jackson himself. I had heard of the Eaton affair in AP American History class, but was unaware of its impact on national politics. It caused Jackson to expel his niece for awhile from the position of White House Hostess (now understood the be the duties of the First Lady), determined who would be Jackson’s party’s successor(the next President), and even led one Cabinet minster to attempt to murder another.

On Style & Presentation:

I was expecting a lively and engaging narrative style was severely disappointed in that regard.  Large swatches of the book are exceedingly dry, and not good about conveying why I should care about its current topic. Some sections were so disjointed that I lost the narrative thread entirely. However, there were a couple chapters that I could not put down.

I also felt he told me about Jackson’s character more than demonstrating Jackson’s character. There are some vignettes to support his opinion of Jackson’s personality. They occurred much later in the book, after I had become annoyed at the overuse of adjectives and under use of examples. I wish he had held off his view of Jackson’s  until the supporting narrative had a chance to appear.

I also wish it had come with a family tree of Jackson’s relations. The many similar names often made it hard to follow who was whom, especially when citing family sources. Which Andrew wrote this particular quote? The man himself, his adopted son, his nephew, or one of his more distant relations?

Bottom line:

  1. Did I learn something?
    1. Yes, about the legal origins of the American Civil War.
    2. I did not learn as much about Jackson’s inner workings as I expected.
  2. Did I enjoy the time spent reading it?
    1. I would say I enjoyed about a third of the book. My friend did not bother finishing it.
  3. Would I recommend it?
    1. To someone trying to understand the evolution of the American presidency and capable of skimming, yes.
    2. To anyone else, no.