Apache Flink: Overkill for Simple, Stateless Stream Processing and ETL?

When discussing stream processing engines, Apache Flink often takes center stage for its advanced capabilities in stateful stream processing and real-time data analytics. However, a common question arises: is Flink too heavyweight for simple, stateless stream processing  and ETL tasks? The short answer for open-source Flink is often yes. But the story evolves significantly when looking at SaaS Flink products such as Confluent Cloud’s Flink offering, with its serverless architecture, multi-tenancy, consumption-based pricing, and no-code/low-code capabilities like Flink Actions. This post explores the considerations and trade-offs to help you decide when Flink is the right tool for your data streaming needs, and when Kafka Streams or Single Message Transform (SMT) within Kafka Connect are the better choice.

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The Nature of Stateless Stream Processing

Stateless stream processing, as the name implies, processes each event independently, with no reliance on prior events or context. This simplicity lends itself to use cases such as filtering, transformations, and simple ETL operations. Stateless tasks are:

• Efficient: They don’t require state management, reducing overhead.
• Scalable: Easily parallelized since there is no dependency between events.
• Minimalistic: Often achievable with simpler, lightweight frameworks like Kafka Streams or Kafka Connect’s Single Message Transforms (SMT).

For example, filtering transactions above a certain amount or transforming event formats for downstream systems are classic stateless tasks that demand minimal computational complexity.

In these scenarios, deploying a robust and feature-rich framework like open-source Apache Flink might seem excessive. Flink’s rich API and state management features are unnecessary for such straightforward use cases. Instead, tools with smaller footprints, and simpler deployment models, such as Kafka Streams, often suffice.

When Flink Feels Like Overkill

Apache Flink is a powerhouse. It’s designed for advanced analytics, stateful processing, and complex event patterns. But this sophistication of the open source framework comes with complexity:

1. Operational Overhead: Setting up and maintaining Flink in an open-source environment can require significant infrastructure and expertise.
2. Resource Intensity: Flink’s distributed architecture and stateful processing capabilities are resource-hungry, often overkill for tasks that don’t require stateful processing.
3. Complexity in Development: The Flink API is robust but comes with a steeper learning curve. The combination with Kafka (or another streaming engine) requires understanding two frameworks. In contrast, Kafka Streams is Kafka-native, offering a single, unified framework for stream processing, which can reduce complexity for basic tasks.

For organizations that need to perform straightforward stateless operations, investing in the full Flink stack can feel like using a sledgehammer to crack a nut. Having said this, FlinkSQL simplifies development for certain personas, providing a more accessible interface beyond just Java and Python.

The Cloud Advantage: Serverless Flink for Everyone

The conversation shifts dramatically with Serverless Flink Cloud offerings, such as Confluent Cloud, which address many of the challenges associated with running open-source Flink. Let’s unpack how Serverless Flink makes a more attractive choice, even for simpler use cases.

1. Serverless Architecture

With a Serverless stream processing service, Flink operates on a fully serverless model, eliminating the need for heavy infrastructure management. This means:

• No Setup Hassles: Developers focus purely on application logic, not cluster provisioning or tuning.
• Elastic Scaling: Resources automatically scale with the workload, ensuring efficient handling of varying traffic patterns without manual intervention. One of the biggest challenges of self-managing Flink is over-provisioning resources to handle anticipated peak loads.  Elastic Scaling mitigates this inefficiency.

2. Multi-Tenancy

Multi-tenant design allows multiple applications, teams or organizations to share the same infrastructure securely. This reduces operational costs and complexity compared to managing isolated clusters for each workload.

3. Consumption-Based Pricing

One of the key barriers to adopting Flink for simple tasks is cost. A truly Serverless Flink offering mitigates this with a pay-as-you-go pricing model:

• You only pay for the resources you use, making it cost-effective for both lightweight and high-throughput workloads.
• It aligns with the scalability of stateless stream processing, where workloads may spike temporarily and then taper off.

4. Bridging the Gap with No-Code and Low-Code Solutions

The rise of citizen integrators and the demand for low-code/no-code solutions have reshaped how organizations approach data streaming. Less-technical users, such as business analysts or operational teams, often face challenges when trying to engage with technical platforms designed for developers.

Low-code/no-code tools address this by providing intuitive interfaces that allow users to build, deploy, and monitor pipelines without deep programming knowledge. These solutions empower business users to take charge of simple workflows and integrations, significantly reducing time-to-value while minimizing the reliance on technical teams.

For example, capabilities like Flink Actions in Confluent Cloud offer a user-friendly approach to deploying stream processing pipelines without coding. By simplifying the process and making it accessible to non-technical stakeholders, these tools enhance collaboration and ensure faster outcomes without compromising performance or scalability. For instance, you can do ETL functions such as transformation, deduplication or masking field:

Fully Managed (SaaS) vs. Partially Managed (PaaS) Cloud Products

When choosing between SaaS and PaaS for data streaming, it’s essential to understand the key differences.

SaaS solutions, like Confluent Cloud, offer a fully managed, serverless experience with automatic scaling, low operational overhead, and pay-as-you-go pricing.

In contrast, PaaS requires users to manage infrastructure, configure scaling policies, and handle more operational complexity.

While many products are marketed as “serverless,” not all truly abstract infrastructure or eliminate idle costs—so scrutinize claims carefully.

SaaS is ideal for teams focused on rapid deployment and simplicity, while PaaS suits those needing deep customization and control. Ultimately, SaaS ensures scalability and ease of use, making it a compelling choice for most modern streaming needs. Always dive into the technical details to ensure the platform aligns with your goals. Don’t trust the marketing slogans of the vendors!

Stateless vs. Stateful Stream Processing: Blurring the Lines

Even if your current use case is stateless, it’s worth considering the potential for future needs. Stateless pipelines often evolve into more complex systems as businesses grow, requiring features like:

• State Management: For event correlation and pattern detection.
• Windows and Aggregations: To derive insights from time-series data.
• Joins: To enrich data streams with contextual information.
• Integrating Multiple Data Sources: To seamlessly combine information from various streams for a comprehensive and cohesive analysis.
• AI/ML Integration: Incorporating machine learning models for real-time inference, enabling intelligent decision-making directly within data streams.

With a SaaS Flink service such as Confluent Cloud, you can start small with stateless tasks and seamlessly scale into stateful operations as needed, leveraging Flink’s full capabilities without a complete overhaul.

When Does Apache Flink Shine?

While Flink may feel like overkill for simple, stateless tasks in its open-source form, its potential is unmatched in these scenarios:

• Enterprise Workloads: Scalable, reliable, and fault-tolerant systems for mission-critical applications.
• Data Integration and Preparation (Streaming ETL): Flink enables preprocessing, cleansing, and enriching data at the streaming layer, ensuring high-quality data reaches downstream systems like data lakes and warehouses.
• Complex Event Processing (CEP): Detecting patterns across events in real time.
• Advanced Analytics: Stateful stream processing for aggregations, joins, and windowed computations.
• AI/ML Integration: Incorporating machine learning models for real-time inference, enabling intelligent decision-making directly within data streams.

Apache Flink for Stateless Stream Processing instead of Kafka Streams or Kafka Connect’s Single Message Transform (SMT)

Stateless stream processing is often achieved using lightweight tools like Kafka Streams or Single Message Transforms (SMTs) within Kafka Connect. SMTs enable inline transformations, such as normalization, enrichment, or filtering, as events pass through the integration framework. This functionality is available in Kafka Connect (provided by Confluent, IBM/Red Hat, Amazon MSK and others) and tools like Benthos for Redpanda. SMTs are particularly useful for quick adjustments and filtering data before it reaches the Kafka cluster, optimizing resource usage and data flow.

While Kafka Streams and Kafka Connect’s SMTs handle many stateless workloads effectively, Apache Flink offers significant advantages for all types of workloads—whether simple or complex, stateless or stateful.

Stream processing in Flink enables true decoupling within the enterprise architecture (as it is not bound to the Kafka cluster like Kafka Streams and Kafka Connect). The benefits are separation of concerns with a domain-driven design (DDD), and improved data governance. And Flink provides interfaces for Java, Python and SQL. Something for (almost) everyone. This makes ideal Flink for ensuring clean, modular architectures and easier scalability.

By processing events from diverse sources and preparing them for downstream consumption, Flink supports both lightweight and comprehensive workflows while aligning with domain boundaries and governance requirements. This brings us to the shift left architecture.

The Shift Left Architecture

No matter what specific use cases you have in mind: The Shift Left Architecture brings data processing upstream with real-time stream processing, transforming raw data into high-quality data products early in the pipeline.

Apache Flink plays a key role as part of a complete data streaming platform by enabling advanced streaming ETL, data curation, and on-the-fly transformations, ensuring consistent, reliable, and ready-to-use data for both operational and analytical workloads, while reducing costs and accelerating time-to-market.

Making the Right Choice for Apache Flink or Not

The decision to use Flink boils down to your use case, expertise, and growth trajectory:

• For basic stateless tasks, consider lightweight options like Kafka Streams or SMTs within Kafka Connect unless you’re already invested in a SaaS such as Confluent Cloud where Flink is also the appropriate choice for simple ETL processes.
• For evolving workloads or scenarios requiring scalability and advanced analytics, a Flink SaaS offers unparalleled flexibility and ease of use.
• For on-premise or edge deployments, Flink’s flexibility makes it an excellent choice for environments where data processing must occur locally due to latency, security, or compliance requirements.

Understanding the deployment environment—cloud, on-premise, or edge— and the capabilities of the Flink product is crucial to choosing the right streaming technology. Flink’s adaptability ensures it can serve diverse needs across these contexts.

Kafka Streams is another excellent, Kafka-native stream processing alternative. Most importantly for this discussion, Kafka Streams is “just” a lightweight Java library, not a server infrastructure like Flink. Hence, it brings different trade-offs with it. I wrote a dedicated article about the trade-offs between Apache Flink and Kafka Streams for stream processing.

Apache Flink’s Role in Your Data Streaming Strategy

In its open-source form, Flink can seem excessive for simple, stateless tasks. However, a serverless Flink SaaS like Confluent Cloud changes the equation. Multi-tenancy and pay-as-you-go pricing make it suitable for a wider range of use cases, from basic ETL to advanced analytics. Serverless features like Confluent’s Flink Actions further reduce complexity, allowing non-technical users to harness the power of stream processing without coding.

Whether you’re just beginning your journey into stream processing or scaling up for enterprise-grade applications, Flink—as part of a complete data streaming platform such as Confluent Cloud—is a future-proof investment that adapts to your needs.

The Data Streaming Landscape 2025 highlights how data streaming has evolved into a key software category, moving from niche adoption to a fundamental part of modern data architecture.

With frameworks like Apache Kafka and Flink at its core, the landscape now spans self-managed, BYOC, and fully managed SaaS solutions, driving real-time use cases, unifying transactional and analytical workloads, and enabling innovation across industries.

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