Part III. Rapid Development
I’ve covered three of the areas that are very important to becoming a web-service (latency, throughput, and quality), and I’m sure this seems daunting or overwhelming. But keep in mind I’m talking about how Mint’s code and service evolved; we didn’t do everything at once because we did not have the resources or the time. As Mint started maturing there were two areas that we stressed:
Manageability: keeping the code and data base clean, and extensible in case features are cut, added, or revised over time. Its very important to start a project thinking about manageability, or how the feature will evolve within the application.
Code manageability: re-factor, don’t introduce a lot of complexity, focus on the tiered architecture to figure out where certain pieces logically fit (e.g. persistence, business logic)
Data base manageability: consider how quickly a data set is going to grow when designing tables, foreign key associations, retrieving data, and frequency with which data is accessed.
Optimization: improving performance of code at runtime in order to satisfy latency and throughput requirements. While this is important, it is not something that one should focus on from the beginning.
- Do not make architectural decisions that are too long term, do what you need for the next 6 months. Why? Because its a startup, the product will continue to evolve in approximately 6 month cycles. Don’t waste time optimizing everything, or before you see a demand for a feature. Remember its a startup; resources are scarce and time is critical.
- e.g. Why we didn’t cache user data from the start? Initially aggregating data nightly because synchronizing data across nodes was difficult and had no mechanism for centralized locking, but once this was put in place we switched to loading data on demand (during user login) and then going through process of aggregating and caching it (in the future we might only show most recent data instead of all data).
- Why we didn’t shard databases from the start? Huge amount of overhead and engineering resources that needed to be allocated more impending issues.
