Why acquire skills & experience in low latency & Big Data? What specific skills are required?

According to Dice’s 2017 Salary Survey (PDF), those tech professionals who specialise in data warehousing, analytics, Big Data, low latency, and machine learning got paid big bucks for the past several years.

More and more organisations are complimenting their data warehouse systems like Teradata with Big Data platforms like Cloudera Data Platform, AWS (i.e. Amazon Web Services) EMR, Microsoft Azure Big Data, Databricks on AWS & Azure, Google Cloud BigQuery, etc.

What specific skills are required?

In the race to secure the best salary in big data engineering & analytics jobs, a single skill development is not enough. Here are some of the skills apart from core Java/Scala/Python, NoSQL, SQL & Unix that will help you transition into a big data engineer/architect:

Q1. Why acquire skills & experience in low latency & Big Data?
A1. 10 years ago Spring & Hibernate were sought after skills, and now a days low latency and Big Data skills are more sought-after as modern applications need to deal with

#1 Response times in milliseconds as opposed to seconds.

#2 Data sizes in Terabytes & Petabytes as opposed to gigabytes. You need to handle not only structured data, but also semi-structured data like log files, event logs, etc and unstructured data like PDFs, Word documents, etc.

#3 Server nodes in 100s with fault-tolerance as opposed to in tens. So be prepared to use terms like the application was deployed to “24 core 100 node cluster in AWS”, etc.

#4 Architectures are 1) highly distributed, 2) event-driven and 3) asynchronous with more complexities requiring good debugging skills. In event-driven architectures there is no single code logic that outlines overall behaviour.

Debugging challenges include

a) Out of order processing issues as events are streamed potentially in out of order from various event sources requiring additional logic.

b) Replay considerations as the master data in the HDFS (i.e. Hadoop Distributed File System) raw zone needs to be rerun in batch modes with renewed access patterns, business logic & rules. Append only systems (E.g. Big Data on HDFS) don’t update data models, but keep appending to the existing data & evaluate the current state by 1) deleting the current data models and 2) replaying the event logs (i.e. the master data). These jobs are run as batch jobs with eventual consistency. This is known as event-sourcing.

c) The NoSQL (i.e. Not Only SQL) databases make development quicker as they are schema-less (i.e. implicit schema), scale rapidly by adding more nodes & handle large volumes of aggregated data (i.e. you store Order, Line Items, and possibly Customer details together as a JSON clob or key-value pairs), which minimizes the number of joins. The NoSQL databases don’t handle ACID (e.g. transaction boundaries, isolation levels, constraints like foreign key, etc) properties, and shift that responsibility to the application layer. This can add more challenges.

d) The data structuring, partitioning & distribution challenges – Skewed data, data shuffling, cartesian join prevention, etc. You will see potential challenges and solutions on the post 15 Apache Spark best practices & performance tuning interview FAQs.

e) Race conditions, performance issues, and out-of-memory issues when dealing with larger volumes of immutable & append-only data logs that need to be replayed into memory or indexed data models for responsiveness & real-time querying.

#5 Deployments & partial service upgrades are more frequent as in once a day or week as opposed to once a month. Micro-services are conducive to frequent & independent upgrades. Some services can be deployed more frequently to more cluster nodes than other services. Deploying to cloud servers like AWS allows you to spin more nodes very quickly to adapt to increasing demand.

Q2. What key words & relevant experiences should you have in your resumes and bring up in your job interviews?
A2. It makes more sense to pay attention to key words like:

real-time processing (i.e. under 200 ms), Near Real Time (i.e. NRT, 200ms to 2 seconds), low latency, event-driven (i.e. react to events or messages), scalable (i.e. react to load by adding more nodes to the cluster), Big Data (i.e. data volume in Terabytes or Petabytes), asynchronous processing, streaming where you process data incrementally as they arrive, Microservices for frequent & independent upgrades, reactive programming where you react to events or messages, responsive (i.e. react to users fast), resilient (i.e. react to failures).

Distributed data storage (E.g. HDFS, AWS S3, etc), computing (E.g. Apache Spark), and messaging (E.g. Apache Kafka) systems with share nothing architecture will be running on 100+ nodes with each node having its own CPU, memory and I/O) and as demand increases more nodes can be added. This is also known as horizontal scaling.

In distributed systems (E.g. NoSQL databases like HBase, Cassandra, etc) the same piece of data is usually replicated to multiple machines to give fault tolerance & high availability. When you update that piece of information on one of the machines, it may take some time (usually milliseconds) to reach every machine that holds the replicated data. This creates the possibility that you might get information that hasn’t yet updated on the replica. In many scenarios, the this anomaly is acceptable. In scenarios where this type of behavior is not acceptable, the NoSQL databases may give the the choice, per transaction, whether data to be eventually consistent or strongly consistent.

In distributed systems the data needs to be partitioned into multiple chunks and placed on different nodes, so that both the read and the write load gets distributed. These chunks are called shards or partitions or vnodes, etc. The partitioning needs to be fair, so that each partition gets a similar load of data. If the partitioning is skewed, a few partitions will handle most of the requests. The partitions which are highly loaded become the bottlenecks for the system, and this is known as hotspotting.

Key Range partitioning is form of partitioning, where you divide the entire keys into continuous ranges and assign each range to a partition. The downside of using key range partitioning is that if the range boundaries are not decided properly, it may lead to hotspots. Key Hash Partitioning is a form of partitioning to apply a hash function on the key which results in a hash value, and then mod it with the number of partitions. The same key will always return the same hash code. The real problem with hash partitioning starts when you change the number of partitions. Consistent Hashing to the rescue where the output range of a hash function is treated as a fixed circular space or “ring”. Each node in the system is assigned a random value within this space which represents its “position” on the ring.

During job interviews bring out these keywords, skills, and experience when responding to open-ended questions like what are some of your recent accomplishments that you are proud of, etc.

Q3. What are some of the buzz words around low latency & Big Data?
A3. Reactive Programming (RP), Lambda Architecture, Kappa Architecture, Event-driven architecture, CAP theorem, Event sourcing, Micro-services, Akka library for scalable applications, Apache Spark libraries based on Akka to process Big Data in both batch and streaming modes, NoSQL databases (E.g. Cassandra, HBase, etc), columnar data formats (E.g. Parquet, ORC, etc), compression algorithms(E.g. LZO, Snappy, LZ4, etc), BigData friendly data formats (E.g. Avro, Parquet, Sequence files, etc), Streaming APIs (E.g. Apache Storm, Apache Spark, StAX, etc), Distributed storage systems (E.g. HDFS, AWS S3, etc), and real-time data pipelines (E.g. Apache Kafka, Amazon Kinesis, etc).

Q4. Why is streaming data in real-time equally important as batch processing?
A4. The reason for this is that processing big volumes of data has to be fast so that a firm can react to changing business conditions in real time. Use cases like fraud detection, identifying data breaches to enhance security, preventative maintenance & making existing processes more efficient requires data in real time and are time critical. General Big Data, Data Science & Data Analytics Interview Q&As.

Q5. Why is it necessary to know Functional Programming (i.e. FP) paradigm?
A5. FP compliments OOP, and can be more robust due to fewer moving parts and fewer or no mutable variables & hidden states if done properly. FP is widely used in Big data, especially in writing Apache Spark jobs in Scala, Python or Java.

1) FP is all about functions, and focuses on computational problems by evaluating functions to transform a collection of data by focusing on the composition and application of functions. For example, you apply “map”, “flatMap”, “reduceByKey”, “groupByKey”, etc to a collection of data.

2) FP favors immutability, which is in line with the modern event sourcing models that replay append only event logs to recompute current state.

3) FP shines in building concurrent applications. OOP languages cannot readily take advantage of multiple processors whereas pure functional programming can run two or more functions at once as functions are not altering outside state.

4) Debugging & testing can be easier. Debugging is easier as pure functions depend only on their input parameters to produce their output. Testing is easier as you don’t have to worry about dealing with hidden state and side effects.

You can learn more about this at Transforming your thinking from OOP to FP, and where does FP shine?.

Functional Programming & Object Oriented Programming in Scala

Q6. Why is it necessary to know CI/CD? i.e. DevOps & DevSecOps?
A6. Traditionally the developers & IT operations work in silos where the developers code, build, test & release the software artefacts and the IT operations deploy & monitor the applications. In DevOps a unified team apply the CI/CD practices with automation tools like Jenkins/Bamboo, Git, Gradle/Maven, Docker/Kubernetes, Ansible/Puppet, and Nagios/Splunk to enable developers & IT operations to continuously build, integrate, test, release, deploy and monitor. This basically requires cultural shift and building of automated pipelines. So, the developers need to have the skills in CI/CD tools.

CIContinuous Integration – code, compile, build, check-in to SCM, unit test, code review and integration test.

CDContinuous Delivery – deploying the application to the test servers for UAT testing.

CDContinuous Deployment- deploying the tested application to the prod server for release.

Continuous Monitoring of CI/CD.

Learn more at Key Area – CI/CD & DevOps

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