How We Built an iOS App, an Android App and a Node.js API in 20 Hours
In this technical retrospective (2012), @govind201 shares practical architectural lessons learned from running, scaling, or migrating production software under lean constraints.
Core Principles for Independent Builders:
Defaulting to simpler architectures (such as monolithic frameworks, SQLite, or managed VPS) prevents early engineering bankruptcy.
Evaluating true compute and egress costs reveals that high cloud bills can often be slashed by 80%+ through judicious re-platforming.
Code you write at 2 AM as a solo engineer must be easy to debug six months later without complex microservice dependencies.
Community Debate Themes:
HN engineers debated the tradeoffs between cloud convenience and raw server economics, database indexing strategies, and resisting premature architectural complexity.
CATEGORY Frugal Engineering →
HISTORICAL ERA Web 2.0 Genesis (2007–2013)
COMMUNITY SCORE 111 points
TOTAL DISCUSSIONS 34 comments
I congratulate them on acheiving your goal of writing an app in such a short time, but I whole-heartedly condemn this app's principle idea. Far from being a force for good it feeds into the incredible paranoia that seems to be prevail in the United States, that everyone is out to get them, and that there are such things as "good areas" and "bad areas".
There are huge problems in justifying this kind of classification, not least because ordinary law abiding citizens who are in a majority also live and work and play in so-called "bad areas" and never suffer crime. What becomes of their house values if such an irresponsible app were to become popular? Their (very) hard earned cash paid as mortgage payments gone to waste.
This app is pernicious in every sense. Even wealthy well-to-do areas can become ghetto-ized: If you tally up the number of burglaries or attempted burglaries in these areas you might find the stats show a different image.
We are not living in some post-apolcolyptic movie world, this is real life and has hard working real people in it, with families and children, who have no choice but to live where they can afford to, and I don't see how this app could ever be considered as "making the world a better place". For who exactly?
This kind of app threatens to push people who live in the targeted areas further down the food chain, and I just wish the developers would have been a bit more socially responsible, in their thought processes.
Rant over. Hopefully a lesson learnt.
The feat of building that kind of app is impressive. I sure as heck can't do it, yet. I do have a few comments, though.
Refine your data classification. On one of your screenshots, you are listing "Arrests" as a type of crime. That's confusing. Also, consider filtering for violent crime rather than crime in general. That would be more in line with the stated purpose of your app.
Realign the usage from a real-time application to a planning application. You don't want your users to be fiddling with a smartphone in a bad neighborhood. That really increases the odds of getting mugged and defeating the purpose of the app.
I agree with some of the other posters that you should tone down the alarmist tone of the app. If nothing else, it's more professional.
Congratulations on your experiment.
I had similar idea whileback so this app is interesting.
What I would change:
1. Remove crime details. They are unnecessary. 2. Replace pins with transparent canvas overlay showing level of danger or safety in shades of red and green. 3. Let user set the desired 'shade of danger'. A simple horizontal or vertical color selector showing shades of red will do. App should buzz every N minutes when users is in area with deeper shade of red unless they press the override button.
That's all.
What's the time function on your graph? Are you only showing the last X weeks or all time? Things like police patrols could affect the frequency of crime over time, and that may change your predictions and confidence intervals.
EDIT: Depending on your data freshness, you may want to do something like push notifications if a crime happened in your area in the past 4 hours. That way if someone walks through a "good area" but there's recent crime they should be more vigilant.
Tip of the hat: you beat me to the punch (though I really wondered about the proper lawyerese for deploying a service like this)...
Of course, the corresponding app, badguy, which alerts would-be criminals to the likely patrol routes of cops, is likely to follow shortly thereafter from the black hats.