Cogini Blog
Featured articles
Deploying an Elixir app to Digital Ocean with mix_deploy Port forwarding with iptables
PayPal Know Your Customer failure
Applying for a merchant account so you can accept credit cards traditionally takes weeks. You meet with the bank, show them your financial statements, and explain your business. Then they make you an offer for e.g. %2.8% + $0.30 per transaction (plus other mystery fees that you find … Read more…
Secure web applications with GraphQL and Elixir
In traditional applications, the web application talks directly to the database. It has rights to do anything, relying on application rules to control access. If an attacker compromises it, then they can do anything, e.g. grab all the data or create a funds transfer transaction. When security is critical … Read more…
Incrementally migrating a legacy app to Phoenix
Over the years we have done lots of projects where we migrated an application from one platform to another. We might do this to solve performance issues or to switch to a better technology stack. This can be a challenge when you have a big app that is in production … Read more…
Abuse and cryptocurrency business models
When I design systems, one of my favorite things is looking at "abuse cases" which define how they behave when confronted by bad actors. I am a big fan of cryptocurrencies. They give us an opportunity to design systems which enforce and incentivize behaviors, e.g. removing risk and rewarding … Read more…
ABC device support and explicit release criteria
One of the most important decisions we make in product development is when to make a release. From a business perspective, it's better to release early and often, with a "minimum viable product". It's also important to define explicit technical quality criteria, or we will waste a lot of resources … Read more…
Anti-pattern: graphical design driven development
Everyone wants to have a beautiful graphical design for their product. The problem comes when graphical design becomes more important than usability and affects the efficiency of the development process. There is an anti-pattern we call "graphical design driven development." The way it goes is that the client starts by … Read more…
Development effort of Android vs iOS
We often need to estimate development projects which have both iOS and Android. It's tempting to say that Android will be the same, but what we have found is that Android takes more effort. The rule of thumb in Silicon Valley is that it takes two to three times the … Read more…
An example of user personas
When we create products, it's important that they help specific users with their issues, not generic users. It's easy to create a list of features, all of which sound good, but don't provide a compelling solution to a specific problem for a specific user. Without that, people won't buy your … Read more…
An example of user stories
User stories are the "Director of Operations" view of the world. They describe step by step how the business works, and what the software needs to do to support it. They should be done after we have defined the user personas, to make sure we are starting from users and … Read more…
Presentation on Elixir performance
Here are the slides for the presentation on performance tuning Elixir I gave to the local Elixir user's group. Read more…