What does an ETL developer do?

We are living in the information age, so information is our main resource, instrument, and goal. Yet, it is not enough to own data, you should know how to work with it. To some extent, data engineers and data scientists replaced treasure hunters, gold miners, and oil producers; they are searching for new ways to collect, process, and store data. With this knowledge, companies can get valuable information.

One of the most well-known ways to work with data is business intelligence, or BI. It is the name of a set of methods and technologies that help to process raw data into useful information. Companies can use this data for various goals, for example, the analysis or development of models for machine learning. The main rule is: this data shouldn’t be in a raw form. The process of preparing useful data is named ETL, which means Extract, Transform, Load. The person who is engaged in this process is an ETL developer.

Let’s take a deeper look at the ETL developer role and the skills it implies. 

ETL developer in simple words

The ETL developer routine consists of three key functions: extract, transform, and load.


Companies can store some information or send it in real-time to various systems. This information is presented in different formats and stored in various software. So, on the Extract stage, an ETL developer should define the needed data sources (CRM, ERP, or third-party software) and gather data from them.


When ETL developers gather data, they transfer it to the Staging Area (temporary storage). In this place, data should be formatted according to the accepted standards. For instance, different financial numerics $31.65 and 0.50 cents will be presented in the same way: $31.65 and $0.50.


Loading structured and formatted data is the final stage of the ETL process. If the quantity of data is small, ETL developers can use any kind of database. The special kind of database that is used for machine learning and processing large parts of data is known as the Data Warehouse.

The Data Warehouse structure is not the same as in the usual database: it consists of several representation tools for supporting data from several dimensions. Also, these tools make the data available for every user. Representation tools are linked with the Warehouse, and users can interact with them in many ways. Representation tools are working instruments of the business intelligence process; they provide analytical data via their dashboards and reporting capabilities.

Before the data gets to the final user, it should go through various technical forms. So, the ETL developer should build this special pipeline for data transfer.

What does the data engineering team look like?

An ETL development team usually consists of software engineers who deal with extracting, processing, and storing data, as well as maintaining the related infrastructure. The data engineering team has a common goal: they need to receive the raw data, define what it should look like to be consumable, make them consumable, and store them. 

The number of team members and their roles depends on the project’s scope, tasks, processing stages, and needed technologies. Let’s consider who can be on the data engineering team.

  • Data architect: he or she can be a member of both the data engineering and the data science team. Data architects plan the infrastructure that data engineers will develop. 
  • Data engineers develop the ecosystem and interfaces to get access to the information.
  • Data analysts analyze and choose methods of data collection, data models, types, and describe the transformation process.
  • Database/Warehouse developers deal with database modeling, development, and maintenance. It can be an SQL database, a data warehouse, or a special type of storage. 
  • Database administrators (DBA) manage databases (if there are several databases), warehouses, or their structure. 
  • Data scientists are usually engaged in projects devoted to machine learning. Sometimes such a project can require several data scientists or even special departments.
  • Business intelligence developers are software engineers that deal with BI interface development.
  • ETL developer is a software engineer, engaged in developing and managing data extraction, transforming and loading processes.

What are the duties of an ETL developer?

We considered ETL developer work in general, but, if we take a deeper look at the responsibilities, we’ll see a lot of processes related to extracting, transforming, and loading. An ETL developer is engaged in data analysis, testing, and managing the system architecture. So, let’s see these tasks in detail: ETL process management, data modeling, database (warehouse) architecture, ETL tools development, and ETL testing.

ETL process management

This is the key stage of data processing and the main ETL developer’s responsibility. Within this stage, a dedicated person or team should use relevant methodologies and technologies so as to:

  • define borders of data processing and identify the ETL process;
  • design the system architecture for data pipeline and its components;
  • write documentation for the system and manage its development;
  • develop and implement ETL tools;
  • test data pipelines and tools.

So, according to the scope of the system, an ETL developer can hold the post of an engineer, a tech lead, a project manager, or a QA engineer of the ETL process. An ETL developer should understand the project’s needs: what data formats it requires, how the data should be loaded (by portions or with dynamic updates), and in what form the data should be presented in the warehouse (it can be OLAP cubes, SQL, NoSQL, Data Marts, and other). During their work, ETL developers can collaborate with other team members to get information about business requirements and final user’s needs.

Data modeling

At the beginning of this task, ETL developers should define what formats the project needs, and then he or she should extract data from their sources. These data formats, called data models, would be presented in the warehouse. 

Business analysts, data analysts, and data scientists create these data models and document them. ETL developers use them to choose the transformation stage and technologies that will be used in formatting.

Database (warehouse) architecture

Warehouse stores structured data. It can consist of data marts that are used for sharing access for related teams to the small parts of data with certain features. For example, if warehouse stores all collected information, data marts contain special kinds of data, it can be website metrics, accounting, etc.

Data marts or warehouses are connected to the end-user interface. This way, users get access to the information and work with it, make queries, or form reports. Data can contain metadata, which can require changes in warehouse architecture. Usually, warehouse development is the task of a warehouse developer, but an ETL developer can also deal with it.

ETL tools development

Data pipeline development is the final stage that goes after protecting system components. The data pipeline represents technical infrastructure and automatically fulfills such tasks as data extraction, data uploading, and data formatting.

Data extraction from the source. ETL tools should be integrated with all systems that store data.

Data uploading into a staging area, the place where data is formatted. Data uploading can also take place in the warehouse, but when ETL developers use an action staging area for this, the process goes faster. 

Data formatting: in the staging area, data is formatted according to relevant standards. Data formatting can consist of several actions:

  1. Data cleansing, the process when ETL developers delete irrelevant data fields;
  2. Data structuring, when specialist should define identify data types and their connections;
  3. Enriching data with metadata that bring useful details.

Loading structured data in the warehouse. ETL developers can load parts of data or constantly update them. Query methods can be needed for addressing the updated data from the data source if ETL specialist deals with dynamic information. If information is static, it can be loaded by portions.

ETL testing

ETL developers should test all technologies involved in the ETL process. So, on this stage, they should:

  • test data models
  • test warehouse architecture
  • verify representation tools
  • validate data flows
  • monitor the speed of uploading, downloading, and querying
  • test system performance

Generally, the QA team and software engineers deal with technical implementation and testing, but certain processes require the participation of ETL developers and data analysts.

To deal with all these tasks, ETL developers represent rich technical skills and related experience. Let’s consider them in detail.

What skills should ETL developers possess?

The field of knowledge of ETL developers involves software engineering and database development experience. So, an ETL developer should know:

ETL tools

There are a lot of special instruments for database development. An ETL developer should be experienced in the usage of this standard software. It can be Talend, Informatica, or Pentaho. They are out-of-the-box tools used for data extraction, transforming, and loading. An ETL developer works as an admin and integrates ETL tools with the software that already works in the company. 

Database (DBA)

An ETL developer should have the data architecture knowledge and understand how SQL/NoSQL databases work and what the warehouse requirements are. ETL developers also deal with data mapping. In addition, ETL specialists should know Hadoop, ETL data integration framework, and platform.

Data analysis principles

ETL developers deal with data modeling, mapping, and formatting, so experience in data analysis is required.

Scripting languages

It will be useful for ETL developers to know some of the most popular scripting languages: Bash, Python, or Perl. This knowledge helps ETL developers use scripts for automation of small parts of the ETL process. It is required in a case with large datasets and complicated pipelines.

Software development

ETL developers should know one of the most popular programming languages that are used in ETL processes. It can be C++, Java, or JavaScript (in case data representation tools work on mobile devices).


ETL developers should provide maintenance and ensure good working conditions for all ETL processes, its system, and tools. So, they require great analytical thinking and troubleshooting skills.

When do you need an ETL developer?

Some technical responsibilities of the ETL developer are equal to what other specialists do, so this position can be replaced with a Warehouse developer or a Business intelligence developer. The company needs an ETL developer to create a large-scale data processing system with complicated data flows. 

In case your system’s work is based on warehouse operations, you need a Warehouse developer as an ETL developer alternative. A warehouse developer can implement data flows and work with data integration tools.

A Business intelligence developer deals with BI interfaces implementation that is based on data pipelines. He or she should provide the maintenance of the system and is needed when your project allows employees to use out-of-the-box solutions and collaborate with business analysts.

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