ELT vs ETL: Unveiling the Differences and Similarities

Nitika Sharma 15 Dec, 2023 • 6 min read


In today’s data-driven world, seamless data integration plays a crucial role in driving business decisions and innovation. Two prominent methodologies have emerged to facilitate this process: Extract, Transform, Load (ETL) and Extract, Load, Transform (ELT). In this article, we will discuss ELT vs ETL, comparing their characteristics, benefits, and suitability for various use cases.

What is ETL?

ETL is a conventional data integration process that involves three sequential steps: Extraction, Transformation, and Loading. In the extraction phase, data is sourced from various systems and databases. This raw data then undergoes transformation, where it is cleaned, formatted, and aggregated to match the target schema. Finally, the transformed data is loaded into a centralized data warehouse for analysis and reporting.  ETL is suitable for scenarios requiring data consolidation from disparate sources into a central repository. It enhances data quality through transformation and cleansing, ensuring accurate reporting and analysis. ETL also enables historical data storage for trend analysis and regulatory compliance.

What is ETL

What is ELT?

ELT is a more modern approach to data integration where the loading of raw data occurs before transformation. With ELT, data is first loaded into a destination storage system, such as a data lake or cloud-based storage, and then transformed as needed for analysis.

ELT is highly suitable for scenarios requiring rapid data insights, such as real-time monitoring, anomaly detection, and predictive analytics. It leverages the scalability of cloud-based storage and processing, ensuring businesses can handle massive data volumes while maintaining responsiveness.

What is ELT

ELT vs ETL: Processes

ETL Process

The ETL process is a traditional data integration method used to move data from various sources to a centralized data warehouse for analysis and reporting. It involves three distinct phases: extraction, transformation, and loading.

  • Extraction: Data is sourced from different systems, databases, APIs, and flat files. These sources can be structured or unstructured. The data is extracted and copied from the source systems to a staging area.
  • Transformation: In this phase, the extracted data undergoes cleaning, validation, enrichment, aggregation, and formatting. The purpose is to ensure that the data is accurate, consistent, and suitable for analysis. Data is transformed into a common format and structure.
  • Loading: The transformed data is loaded into a centralized data warehouse, where it’s organized, indexed, and stored for reporting and analysis. Loading can be incremental (only new or changed data) or full (entire dataset).
ETL Process

ELT Process

ELT is a more modern approach to data integration, where the loading of raw data into a target storage system happens before the transformation. This approach is often used with data lakes, cloud-based storage, and distributed systems.

  • Extraction: Similar to ETL, data is extracted from various sources. However, in ELT, the raw data is directly loaded into the target storage system, such as a data lake or cloud-based repository.
  • Loading: After extraction, data is loaded into the target storage without significant transformation. Loading can be done in near real-time, allowing for continuous ingestion of data.
  • Transformation: Transformation takes place post-loading. Data is transformed within the target storage environment using distributed processing and tools designed for big data analytics. Transformation can include cleaning, filtering, enrichment, and aggregation.
ETL vs ELT Process

Pros and Cons

Pros and Cons of ELT

ELT Pros

  • Flexible Data Formats: ELT paired with a data lake accepts data of all formats.
  • Speed of Loading: There is immediate access to data after extraction because the data transformation occurs after loading.
  • High Data Availability: Data is always available because data load goes to the data lake. Tools (that don’t necessarily need structured data) can easily access these data instantly instead of waiting until data transformation.
  • Efficiency: Since data transformation usually occurs during analysis, in contrast to converting all the data before loading, resource use is better.

ELT Cons

  • The flexibility of Environment: Harnessing the advantage of ELT requires pairing with cloud-based processing power and storage.
  • Compliance: ELT’s integration with the cloud raises unease about data privacy because several regulations are against data storage on servers outside specific borders.
  • New Approach: As ELT is recent in its development and after cloud computing has attained maturity, it does not have the backing of a large community behind it. Yet.

Pros and Const of ETL

ETL Pros

  • Fast Analysis: After ETL rearranges and transforms the data, data queries gain rapidity and efficiency, unlike unstructured data.
  • Compliance: To assure compliance with data privacy rules, ETL encrypts or removes sensitive data before loading them into the data warehouse.
  • Environment Flexibility: implementation of ETL can be done on-site or in a cloud-based environment. ETL can take data from on-site systems and load them to a cloud database.

ETL Cons

  • Rigid Workflow: Modifying the schema of the data warehouse may occur if the warehouse’s data layout does not support valuable new queries.
  • Speed: As the ETL process involves a transformation in an area before loading, it is not directly available for use in contrast to the ELT, which is immediately available after extraction.
  • Data Volume: ETL is unsuitable for handling large volumes of data because data transformation is time-consuming. It is perfect for smaller data sets that need more maneuvers because they provide crucial data for analysis.

Key Differences Between ELT vs ETL

Order of ProcessExtract, Transform, LoadExtract, Load, Transform
FlexibilitySince ETL always follows a linear process, it is inflexible.As transformation is undefined from the start, it leads to a more flexible process.
Source DataStores structured data.Supports structured, semi-structured, and unstructured data.
Storage TypeFunction on-site or through the cloud.Performs better with cloud data warehouses.
Data sizeSuitable for small data sets.Suitable for sizeable data sets.
ScalabilityLow.High and can be configured to fit changing data sources.
Storage RequirementLow since only the data that transforms goes into storage.Due to the storage of raw data, the storage requirement is usually high.
Hardware RequirementThe hardware usually assists in carrying out transformation.ELT tools usually employ the use of available computing powers to convert data.
Complexity of TransformationData integration professionals with experience in ETL code transformations in the tool.Programmers write transformations (using Java, for example), and the converted data needs maintenance.
SkillsPerforming extraction, transformation, and loading require training and skills.Since ELT relies primarily on native DBMS functionality, existing skills are applicable.
SuitabilityAnalysts and Data Scientists.SQL coders and report reading users.

Data Transformation

In ETL, data transformation occurs mid-process, often leading to upfront delays. ELT, on the other hand, transforms data post-loading, enabling quicker data availability and reducing latency. However, ETL’s upfront transformation facilitates cleaner data storage and reporting.

Data Volume and Speed

ETL processes data in batches, while ELT can handle continuous streams of data. ELT excels in processing big data streams at scale, providing real-time insights for dynamic decision-making.

Data Storage and Architectures

ETL typically uses a structured data warehouse, while ELT embraces more modern approaches like data lakes and cloud storage. ELT’s flexible architecture suits the evolving needs of cloud-based and distributed systems.

ELT vs ETL: Choosing the Right Approach

Factors Influencing the Choice

When deciding between ETL and ELT, factors like data volume, processing speed, infrastructure, and business objectives play a crucial role. Organizations should align their choice with their data integration needs and technological capabilities.

Hybrid Approaches

Hybrid solutions that combine ETL and ELT elements offer flexibility and optimization. Organizations can leverage the strengths of each approach for various use cases, achieving a balance between upfront transformation and real-time insights.

Future Trends in Data Integration

The data integration landscape continues to evolve, with emerging trends such as serverless computing and AI-driven data preparation. As technology advances, ETL and ELT approaches will likely adapt to meet the demands of the digital age.


In the realm of data integration, choosing between ETL vs ELT involves understanding the nuances of each approach. ETL’s structured transformation suits certain scenarios, while ELT’s real-time processing excels in others. The key is to align your choice with your organization’s goals and technological landscape, ensuring optimal data integration and insights for informed decision-making.

For those seeking to deepen their expertise in data analytics and integration, consider exploring the Analytics Vidhya’s Blackbelt program, which offers comprehensive training to sharpen your skills and stay ahead in the evolving world of data-driven insights and decision-making.

Frequently Asked Questions

Q1. What’s the difference between ETL and ELT?

A. ETL involves data extraction, transformation, and loading in that order, often used for structured data. ELT loads raw data first, then transforms it, suitable for real-time analytics and big data processing.

Q2. Which is better ETL or ELT?

A. The choice between ETL and ELT depends on factors like data volume, processing speed, and infrastructure. ETL is beneficial for structured data warehousing, while ELT excels in real-time insights and scalability for modern data storage.

Q3. Is ELT replacing ETL?

A. ELT is not entirely replacing ETL; rather, it’s a complementary approach. ELT’s suitability for big data and real-time analytics has made it a preferred choice in certain scenarios, while ETL still holds value for structured data transformations.

Q4. What is the difference between ETL and ELT stack?

A. ETL stack focuses on data transformation before loading into a target repository, such as a data warehouse. ELT stack, however, loads data first into storage, like a data lake, and then performs transformations, aligning with modern cloud-based and big data architectures.

Nitika Sharma 15 Dec 2023

Frequently Asked Questions

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