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EPL (Event Processing Language) is a high-level programming language specifically designed for complex event processing (CEP). Developed by EsperTech, it allows users to process and analyze multiple streams of data in real-time. EPL's syntax is similar to SQL, making it easily accessible for developers familiar with database querying. Its primary use lies in scenarios where vast amounts of streaming data need to be processed quickly and efficiently, such as financial services or IoT applications. The language has been open-source since its inception, promoting widespread adoption across various industries.

Ask the right questions secure the right EPL (Event Processing Language) talent among an increasingly shrinking pool of talent.

First 20 minutes

General EPL (Event Processing Language) app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in EPL (Event Processing Language) application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What are the basic components of an EPL statement?

The basic components of an EPL statement are: Event Stream, Filter, Window, Output, and Pattern.

How would you define an event in EPL?

In EPL, an event is defined as an occurrence of a specific action or a change in state. It can be represented as a data object with a set of properties.

Describe the difference between 'window' and 'retain-union' in EPL.

'Window' is used to hold the last N events for a period of time, while 'retain-union' is used to hold all events from both named windows until they are explicitly deleted.

What is the purpose of the 'insert into' statement in EPL?

The 'insert into' statement in EPL is used to insert events into a named window or stream.

How would you use the 'group by' clause in EPL?

The 'group by' clause in EPL is used to group events by one or more properties. It is often used with aggregation functions to perform calculations on each group of events.

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What you’re looking for early on

Does the candidate have a strong understanding of EPL?

Has the candidate demonstrated problem-solving skills?

Can the candidate work well in a team?

Does the candidate have experience with real-time event processing?

Next 20 minutes

Specific EPL (Event Processing Language) development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

What are the different types of windows in EPL and how are they used?

The different types of windows in EPL are: Sliding Window, Tumbling Window, and Batch Window. They are used to hold events for a period of time or until a certain condition is met.

How would you handle complex event processing in EPL?

Complex event processing in EPL can be handled using patterns and subqueries to detect complex sequences of events and perform calculations on them.

What is the role of the 'having' clause in EPL?

The 'having' clause in EPL is used to filter the results of a 'group by' clause based on a condition. It is similar to the 'where' clause, but operates on the results of aggregations.

Describe the difference between 'every' and 'every-distinct' in EPL.

'Every' is used to match every occurrence of an event, while 'every-distinct' is used to match every distinct occurrence of an event based on one or more properties.

How would you use the 'merge' statement in EPL?

The 'merge' statement in EPL is used to update, insert, or delete events in a named window or stream based on a condition.

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At this point, a skilled EPL (Event Processing Language) engineer should demonstrate strong problem-solving abilities, proficiency in EPL (Event Processing Language) programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with EPL (Event Processing Language).

What does this simple EPL statement do?
select * from StockTick
This statement selects all events from the 'StockTick' event stream.
What does this EPL statement do?
select avg(price) from StockTick.win:time(30 sec)
This statement calculates the average price of the 'StockTick' events in the last 30 seconds.
What does this EPL statement do?
select * from pattern [every a=StockTick -> b=StockTick(a.symbol = b.symbol and a.price < b.price)]
This statement selects all pairs of 'StockTick' events where the second event has the same symbol as the first and a higher price.
What does this EPL statement do?
select * from StockTick#unique(symbol) retain-union
This statement selects the most recent event for each unique symbol from the 'StockTick' event stream and retains all unique events.

Wrap-up questions

Final candidate for EPL (Event Processing Language) Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle EPL (Event Processing Language) application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the different types of joins in EPL and how are they used?

The different types of joins in EPL are: Inner Join, Outer Join, and Full Join. They are used to combine events from two or more streams based on a condition.

How would you handle time-based events in EPL?

Time-based events in EPL can be handled using time windows, timers, and temporal patterns to process events based on their timestamps.

What is the role of the 'context' statement in EPL?

The 'context' statement in EPL is used to define a context under which certain EPL statements should be executed. It allows for more granular control over event processing.

EPL (Event Processing Language) application related

Product Perfect's EPL (Event Processing Language) development capabilities

Beyond hiring for your EPL (Event Processing Language) engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in EPL (Event Processing Language) projects, and can engage in multiple capacities.

EPL (Event Processing Language) Consultive assessments

EPL (Event Processing Language) Application Conversion Assessment EPL (Event Processing Language) Application Integration Assessment EPL (Event Processing Language) Data & Database Integration Assessment

Custom EPL (Event Processing Language) development projects

Custom EPL (Event Processing Language) App Conversion EPL (Event Processing Language) Custom App Development Process App UI Design for EPL (Event Processing Language) Facelifts

Hiring guide for EPL (Event Processing Language) Engineers

EPL (Event Processing Language) Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the EPL (Event Processing Language) engineer at this point.

EPL (Event Processing Language) Consultive assessments

Custom EPL (Event Processing Language) development projects