Gwen Shapira

Gwen Shapira is a Solutions Architect at Cloudera and leader of IOUG Big Data SIG. She studied computer science, statistics, and operations research at the University of Tel Aviv, and then went on to spend the next 15 years in different technical positions in the IT industry. She specializes in scalable and resilient solutions, and helps her customers build high-performance large-scale data architectures using Hadoop. Gwen Shapira is a frequent presenter at conferences and regularly publishes articles in technical magazines and her blog.

Validating data models with Kafka-based pipelines

A case for back-end A/B testing.

Start the O’Reilly “Introduction to Apache Kafka” training video for free. In this video, Gwen Shapira shows developers and administrators how to integrate Kafka into a data processing pipeline.

A/B testing is a popular method of using business intelligence data to assess possible changes to websites. In the past, when a business wanted to update its website in an attempt to drive more sales, decisions on the specific changes to make were driven by guesses; intuition; focus groups; and ultimately, which executive yelled louder. These days, the data-driven solution is to set up multiple copies of the website, direct users randomly to the different variations and measure which design improves sales the most. There are a lot of details to get right, but this is the gist of things.

When it comes to back-end systems, however, we are still living in the stone age. Suppose your business grew significantly and you notice that your existing MySQL database is becoming less responsive as the load increases. Suppose you consider moving to a NoSQL system, you need to decide which NoSQL solution to pick — there are a lot of options: Cassandra, MongoDB, Couchbase, or even Hadoop. There are also many possible data models: normalized, wide tables, narrow tables, nested data structures, etc.

A/B testing multiple data stores and data models in parallel

It is surprising how often a company will pick a solution based on intuition or even which architect yelled louder. Rather than making a decision based on facts and numbers regarding capacity, scale, throughput, and data-processing patterns, the back-end architecture decisions are made with fuzzy reasoning. In that scenario, what usually happens is that a data store and a data model are somehow chosen, and the entire development team will dive into a six-month project to move their entire back-end system to the new thing. This project will inevitably take 12 months, and about 9 months in, everyone will suspect that this was a bad idea, but it’s way too late to do anything about it. Read more…

The problem of managing schemas

Schemas inevitably will change — Apache Avro offers an elegant solution.


When a team first starts to consider using Hadoop for data storage and processing, one of the first questions that comes up is: which file format should we use?

This is a reasonable question. HDFS, Hadoop’s data storage, is different from relational databases in that it does not impose any data format or schema. You can write any type of file to HDFS, and it’s up to you to process it later.

The usual first choice of file formats is either comma delimited text files, since these are easy to dump from many databases, or JSON format, often used for event data or data arriving from a REST API.

There are many benefits to this approach — text files are readable by humans and therefore easy to debug and troubleshoot. In addition, it is very easy to generate them from existing data sources and all applications in the Hadoop ecosystem will be able to process them. Read more…