The Evolution of a Scrappy Startup to a Successful Web Service

The Evolution of a Scrappy Startup to a Successful Web Service
PoornimaVijayashanker – Software Engineer
November 7, 2008

What is Mint.com?
My Bio
Came up with the name and the second employee
Getting Mint.com off the ground
Used open source tools: Eclipse, mySQL, Apache Tomcat
No prior experience at a startup or in web services
Mint.com today

Creating a prototype
Prototype:
a rudimentary working model of a product or information system, build for demonstration purposes or as part of the development process.

What doesn’t belong in a prototype?
Don’t waste time spec’ing out a complete feature set
“Everyone by now presumably knows about the danger of premature optimization. I think we should be just as worried about premature design - designing too early what a program should do. “
Paul Graham
Mint.com’s mission statement: “Do more with your money.”
Aggregate checking, savings, and credit card accounts
Show balances
Auto-categorize transactions

What does belong in a prototype.
Started small by focusing on features that differentiated our product
Focus on solving critical user problems. Engineering problems arise from their solutions.
e.g. Financial data is a sensitive matter, needed a good security model.
Handle concurrency amongst our 100+ users, and making sure we were encrypting stored data.
Bare-bones implementation for algorithms is sufficient. Don’t get tied down to any one particular solution. Refine in subsequent releases and based on product specifications.
Simple unit test framework, no system tests; focus was to get the product out there and have real users test it with real data!

What did our application server look like?
Single Server
Web layer and analysis engine, wired together using RMI.
UI -> Business Logic -> Data processing engines
Single data base that consisted of less than 50 tables

What did our code base look like?
A few key choices during prototyping molded our software’s architecture, and affected the longevity of our code base
e.g. Choice in messaging system: JMS, RMI, or none
Re-factored code into logical modules to avoid spaghetti code, a task that would have been much harder to do later on, especially with a growing team and code base.

Web Application to Web Service
Prototype -> Product likened to Web Application to Web Service.
Application is a point tool used to complete a simple tasks
Web services is more than features
Goal is to create a product with growing user base you have to broaden thinking from features to logistics

Prime mover of Software’s Architecture
User Growth Rate
To solve the business problem of becoming profitable you have to grow the user base
More users -> Growing Pains
Need to be addressed in a timely manner in order to continue to grow and keep the existing users happy.

Computer Architecture 101
Latency: a reasonable response time
Throughput: satisfying many requests without compromising latency
Quality: accurate data and reliable service
Address points of failure

How do you achieve each?
Latency: affected by amount of data that needs to be retrieved, in order to satisfy the incoming requests.
e.g. computed data and persisted to db, as users increased reading/writing to the db took forever.
Switched to loading user data into a cache upon login and then computing.

Throughput: handle multiple requests/processes
Separate into code into tiers (UI, web, business/service logic, DAO, db) in parallel data processing/retrieving tier
Separate data engine from web engine
One server for handling data processing
One server to process user requests and serve user pages
Tune each server based on its needs (web vs. analysis)

Quality: low bug count, which is directly proportional to incoming number of customer service requests
Testing (unit, load, and system)
Beware of the vocal minority, by measuring the number of users impacted by a bug.

Optimization: improving performance of code at runtime in order to satisfy latency and throughput requirements.
“…premature optimization is the root of all evil." – Donald Knuth

How to Measure
Created internal tools to measure the performance of our code base, which helps figure out where to optimize.
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.

What to measure
How quickly a data set is going to grow when designing tables, foreign key associations, retrieving data, and frequency with which data is accessed
Sharding: break up a large database into smaller pieces that contains redundant information or a parent db can map data to separate dbs.
Implementation was based on user id lookup
Easy to shard because we were dealing with financial data that is restricted to a single person, each user and their data was limited to a single shard, unless services like Twitter or Facebook that have lots of interactions amongst users

Review Decisions
We didn’t cache user data from the start 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
We didn't shard databases from the start because of overhead and more impending issues.
In the future we might only show most recent data instead of all data).

Summary
Prototype with limited features
Addressing CS 101 Basics: Latency, Throughput, and Quality
Making architectural decisions based on the time frame
Measure and Optimize that which is critical
Check it out: www.mint.com
My blog: www.femgineer.com

The Evolution of a Scrappy Startup to a Successful Web Service

by Poornima Vijayashanker on Aug 22, 2009

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The Evolution of a Scrappy Startup to a Successful Web Service — Presentation Transcript