Showing 1–11 of 11 results for author: Carl, N

Large-scale workflow placement in serverless computing using integer nonlinear programming

Authors: Joshua Adamek, Natalie Carl, Trever Schirmer, Moritz Heinlein, David Bermbach, Sergio Lucia

Abstract: Serverless edge computing has become a powerful cloud framework that enables the execution of large workflows without the need for the user to manage the underlying servers and edge devices. In this work, we address the challenge of deploying these workflows on a large number of different existing servers and edge devices such that monetary costs for the users and workflow evaluation times are min… ▽ More Serverless edge computing has become a powerful cloud framework that enables the execution of large workflows without the need for the user to manage the underlying servers and edge devices. In this work, we address the challenge of deploying these workflows on a large number of different existing servers and edge devices such that monetary costs for the users and workflow evaluation times are minimized. To this end, the workflow and cloud node attributes are modeled in a mathematical framework. As a result, we present a novel model of the optimal placement problem as a nonlinear integer program. To solve both the issues of scaling towards a larger number of cloud/edge nodes as well as decomposed knowledge of node attributes, we propose a novel decomposition strategy. In a case study, we show the beneficial scaling properties of the decomposition approach and a mean improvement of 10% against a simple deployment heuristic. △ Less

Submitted 14 August, 2026; originally announced August 2026.

Comments: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible

New Kids: An Architecture and Performance Investigation of Second-Generation Serverless Platforms

Authors: Trever Schirmer, Aris Wiegand, Lucca di Benedetto, Linus Gustafsson, Natalie Carl, Tobias Pfandzelter, David Bermbach

Abstract: With the ever-increasing usage of serverless computing in both industry and academia, it is essential to understand the mechanisms that power the underlying platforms. As serverless is more than ten years old, there are different platforms with vastly different approaches. We show that, next to the traditional and popular platforms, a second generation of serverless platform has emerged. While fir… ▽ More With the ever-increasing usage of serverless computing in both industry and academia, it is essential to understand the mechanisms that power the underlying platforms. As serverless is more than ten years old, there are different platforms with vastly different approaches. We show that, next to the traditional and popular platforms, a second generation of serverless platform has emerged. While first-generation platforms are based on containerized, centralized execution, the new generation leverages lightweight isolates and edge deployment. This evolution reduces warm request latency from approximately 40ms to around 10ms and reduces cold starts to an afterthought, but limits the execution environment. In this paper, we gather and analyze all publicly available information to provide detailed insights into the underlying architecture of seven platforms and then run a microbenchmark-based evaluation totaling more than 38 million function calls to gain a deeper understanding their performance. △ Less

Submitted 14 August, 2026; v1 submitted 17 April, 2026; originally announced April 2026.

Comments: Author version of paper accepted in ACM Transactions on Internet Technology, 30 pages

GeoBenchr: An Application-Centric Benchmarking Suite for Spatiotemporal Database Platforms

Authors: Tim C. Rese, Nils Japke, Diana Baumann, Natalie Carl, David Bermbach

Abstract: The rapid growth of spatiotemporal data volumes needs to be handled by database systems capable of efficiently managing and querying such data. Existing systems such as PostGIS, SpaceTime, and MobilityDB offer partial solutions but differ widely in scope and performance. Also, first spatiotemporal benchmarks provide valuable insights but are limited in scope and, to our knowledge, no application-c… ▽ More The rapid growth of spatiotemporal data volumes needs to be handled by database systems capable of efficiently managing and querying such data. Existing systems such as PostGIS, SpaceTime, and MobilityDB offer partial solutions but differ widely in scope and performance. Also, first spatiotemporal benchmarks provide valuable insights but are limited in scope and, to our knowledge, no application-centric benchmarking suite exists. In this paper, we propose GeoBenchr, an open-source, application-centric benchmarking suite for spatiotemporal platforms. GeoBenchr enables comprehensive evaluation across diverse datasets, query types, and workload patterns, reflecting realistic use cases from domains such as cycling, aviation, and maritime tracking. We use our GeoBenchr prototype to evaluate several system aspects including scalability, configuration impact, and cross-platform performance comparison. Our results highlight the importance of application-centric benchmarking in selecting suitable spatiotemporal database systems for real-world scenarios. △ Less

Submitted 30 April, 2026; v1 submitted 10 March, 2026; originally announced March 2026.

Comments: Accepted for publication at The 27th IEEE International Conference on Mobile Data Management

Provuse: Platform-Side Function Fusion for Performance and Efficiency in FaaS Environments

Authors: Niklas Kowallik, Natalie Carl, Leon Pöllinger, Wei Wang, Sharan Santhanam, David Bermbach

Abstract: Function-as-a-Service (FaaS) platforms provide scalable and cost-efficient execution but suffer from increased latency and resource overheads in complex applications comprising multiple functions, particularly due to double billing when functions call each other. This paper presents Provuse, a transparent, platform-side optimization that automatically performs function fusion at runtime for indepe… ▽ More Function-as-a-Service (FaaS) platforms provide scalable and cost-efficient execution but suffer from increased latency and resource overheads in complex applications comprising multiple functions, particularly due to double billing when functions call each other. This paper presents Provuse, a transparent, platform-side optimization that automatically performs function fusion at runtime for independently deployed functions, thereby eliminating redundant function instances. This approach reduces both cost and latency without requiring users to change any code. Provusetargets provider-managed FaaS platforms that retain control over function entry points and deployment artifacts, enabling transparent, runtime execution consolidation without developer intervention. We provide two implementations for this approach using the tinyFaaS platform as well as Kubernetes, demonstrating compatibility with container orchestration frameworks. An evaluation shows consistent improvements, achieving an average end-to-end latency reduction of 26.33% and a mean RAM usage reduction of 53.57%. These results indicate that automatic function fusion is an effective platform-side strategy for reducing latency and RAM consumption in composed FaaS applications, highlighting the potential of transparent infrastructure-level optimizations in serverless systems. △ Less

Submitted 10 March, 2026; v1 submitted 6 March, 2026; originally announced March 2026.

Comments: Accepted for publication at the 4th Workshop on SErverless Systems, Applications and MEthodologies (SESAME '26)

Serverless Abstractions for Short-Running, Lightweight Streams

Authors: Natalie Carl, Niklas Kowallik, Constantin Stahl, Trever Schirmer, Tobias Pfandzelter, David Bermbach

Abstract: Serverless computing and stream processing represent two dominant paradigms for event-driven data processing, yet both make assumptions that render them inefficient for short-running, lightweight, and unpredictable streams that require stateful processing. We propose stream functions as a novel extension of the Function-as-a-Serivce model that treat short streams as the unit of execution, state, a… ▽ More Serverless computing and stream processing represent two dominant paradigms for event-driven data processing, yet both make assumptions that render them inefficient for short-running, lightweight, and unpredictable streams that require stateful processing. We propose stream functions as a novel extension of the Function-as-a-Serivce model that treat short streams as the unit of execution, state, and scaling. Stream functions process streams via an iterator-based interface, enabling seamless inter-event logic while retaining the elasticity and scale-to-zero capabilities offered by serverless platforms. Our evaluation shows that stream functions reduce the processing overhead by ~99 % compared to a mature stream process- ing engine in a video-processing use case. By providing comparable performance to serverless functions with stream semantics, stream functions provide an effective and efficient abstractions for a class of workloads underserved by existing models. △ Less

Submitted 3 March, 2026; originally announced March 2026.

Comments: Accepted for publication at the 4th Workshop on SErverless Systems, Applications and MEthodologies (SESAME '26)

Towards Energy-Efficient Serverless Computing with Hardware Isolation

Authors: Natalie Carl, Tobias Pfandzelter, David Bermbach

Abstract: Serverless computing provides just-in-time infrastructure provisioning with rapid elasticity and a finely-grained pricing model. As full control of resource allocation is in the hands of the cloud provider and applications only consume resources when they actually perform work, we believe that serverless computing is uniquely positioned to maximize energy efficiency. However, the focus of curren… ▽ More Serverless computing provides just-in-time infrastructure provisioning with rapid elasticity and a finely-grained pricing model. As full control of resource allocation is in the hands of the cloud provider and applications only consume resources when they actually perform work, we believe that serverless computing is uniquely positioned to maximize energy efficiency. However, the focus of current serverless platforms is to run hundreds or thousands of serverless functions from different tenants on traditional server hardware, requiring expensive software isolation mechanisms and a high degree of overprovisioning, i.e., idle servers, to anticipate load spikes. With shared caches, high clock frequencies, and many-core architectures, servers today are optimized for large, singular workloads but not to run thousands of isolated functions. We propose rethinking the serverless hardware architecture to align it with the requirements of serverless software. Specifically, we propose using hardware isolation with individual processors per function instead of software isolation resulting in a serverless hardware stack that consumes energy only when an application actually performs work. In preliminary evaluation with real hardware and a typical serverless workload we find that this could reduce energy consumption overheads by 90.63% or an average 70.8MW. △ Less

Submitted 9 October, 2025; originally announced October 2025.

Multi-Event Triggers for Serverless Computing

Authors: Natalie Carl, Trever Schirmer, Niklas Kowallik, Joshua Adamek, Tobias Pfandzelter, Sergio Lucia, David Bermbach

Abstract: Function-as-a-Service (FaaS) is an event-driven serverless cloud computing model in which small, stateless functions are invoked in response to events, such as HTTP requests, new database entries, or messages. Current FaaS platform assume that each function invocation corresponds to a single event. However, from an application perspective, it is desirable to invoke functions in response to a colle… ▽ More Function-as-a-Service (FaaS) is an event-driven serverless cloud computing model in which small, stateless functions are invoked in response to events, such as HTTP requests, new database entries, or messages. Current FaaS platform assume that each function invocation corresponds to a single event. However, from an application perspective, it is desirable to invoke functions in response to a collection of events of different types or only with every n\textsuperscript{th} event. To implement this today, a function would need additional state management, e.g., in a database, and custom logic to determine whether its trigger condition is fulfilled and the actual application code should run. In such an implementation, most function invocations would be rendered essentially useless, leading to unnecessarily high resource usage, latency, and cost for applications. In this paper, we introduce multi-event triggers, through which complex conditions for function invocations can be specified. Specifically, we introduce abstractions for invoking functions based on a set of $n$ events and joins of multiple events of different types. This enables application developers to define intricate conditions for function invocations, workflow steps, and complex event processing. Our evaluation with a proof-of-concept prototype shows that this reduces event--invocation latency by 62.5\% in an incident detection use-case and that our system can handle more than 300,000 requests per second on limited hardware, which is sufficient load for implementation in large FaaS platforms. △ Less

Submitted 11 October, 2025; v1 submitted 27 May, 2025; originally announced May 2025.

Comments: Accepted for publishing at IC2E'25

Minos: Exploiting Cloud Performance Variation with Function-as-a-Service Instance Selection

Authors: Trever Schirmer, Natalie Carl, Nils Höller, Tobias Pfandzelter, David Bermbach

Abstract: Serverless Function-as-a-Service (FaaS) is a popular cloud paradigm to quickly and cheaply implement complex applications. Because the function instances cloud providers start to execute user code run on shared infrastructure, their performance can vary. From a user perspective, slower instances not only take longer to complete, but also increase cost due to the pay-per-use model of FaaS services… ▽ More Serverless Function-as-a-Service (FaaS) is a popular cloud paradigm to quickly and cheaply implement complex applications. Because the function instances cloud providers start to execute user code run on shared infrastructure, their performance can vary. From a user perspective, slower instances not only take longer to complete, but also increase cost due to the pay-per-use model of FaaS services where execution duration is billed with microsecond accuracy. In this paper, we present Minos, a system to take advantage of this performance variation by intentionally terminating instances that are slow. Fast instances are not terminated, so that they can be re-used for subsequent invocations. One use case for this are data processing and machine learning workflows, which often download files as a first step, during which Minos can run a short benchmark. Only if the benchmark passes, the main part of the function is actually executed. Otherwise, the request is re-queued and the instance crashes itself, so that the platform has to assign the request to another (potentially faster) instance. In our experiments, this leads to a speedup of up to 13% in the resource intensive part of a data processing workflow, resulting in up to 4% faster overall performance (and consequently 4% cheaper prices). Longer and complex workflows lead to increased savings, as the pool of fast instances is re-used more often. For platforms exhibiting this behavior, users get better performance and save money by wasting more of the platforms resources. △ Less

Submitted 24 October, 2025; v1 submitted 19 May, 2025; originally announced May 2025.

Comments: Accepted for Publication at the 13th IEEE International Conference on Cloud Engineering (IC2E 2025)

Superhuman performance in urology board questions by an explainable large language model enabled for context integration of the European Association of Urology guidelines: the UroBot study

Authors: Martin J. Hetz, Nicolas Carl, Sarah Haggenmüller, Christoph Wies, Maurice Stephan Michel, Frederik Wessels, Titus J. Brinker

Abstract: Large Language Models (LLMs) are revolutionizing medical Question-Answering (medQA) through extensive use of medical literature. However, their performance is often hampered by outdated training data and a lack of explainability, which limits clinical applicability. This study aimed to create and assess UroBot, a urology-specialized chatbot, by comparing it with state-of-the-art models and the per… ▽ More Large Language Models (LLMs) are revolutionizing medical Question-Answering (medQA) through extensive use of medical literature. However, their performance is often hampered by outdated training data and a lack of explainability, which limits clinical applicability. This study aimed to create and assess UroBot, a urology-specialized chatbot, by comparing it with state-of-the-art models and the performance of urologists on urological board questions, ensuring full clinician-verifiability. UroBot was developed using OpenAI's GPT-3.5, GPT-4, and GPT-4o models, employing retrieval-augmented generation (RAG) and the latest 2023 guidelines from the European Association of Urology (EAU). The evaluation included ten runs of 200 European Board of Urology (EBU) In-Service Assessment (ISA) questions, with performance assessed by the mean Rate of Correct Answers (RoCA). UroBot-4o achieved an average RoCA of 88.4%, surpassing GPT-4o by 10.8%, with a score of 77.6%. It was also clinician-verifiable and exhibited the highest run agreement as indicated by Fleiss' Kappa (k = 0.979). By comparison, the average performance of urologists on board questions, as reported in the literature, is 68.7%. UroBot's clinician-verifiable nature and superior accuracy compared to both existing models and urologists on board questions highlight its potential for clinical integration. The study also provides the necessary code and instructions for further development of UroBot. △ Less

Submitted 4 June, 2024; v1 submitted 3 June, 2024; originally announced June 2024.

Journal ref: 10.1016/j.esmorw.2024.100078

GeoFF: Federated Serverless Workflows with Data Pre-Fetching

Authors: Natalie Carl, Trever Schirmer, Tobias Pfandzelter, David Bermbach

Abstract: Function-as-a-Service (FaaS) is a popular cloud computing model in which applications are implemented as work flows of multiple independent functions. While cloud providers usually offer composition services for such workflows, they do not support cross-platform workflows forcing developers to hardcode the composition logic. Furthermore, FaaS workflows tend to be slow due to cascading cold starts,… ▽ More Function-as-a-Service (FaaS) is a popular cloud computing model in which applications are implemented as work flows of multiple independent functions. While cloud providers usually offer composition services for such workflows, they do not support cross-platform workflows forcing developers to hardcode the composition logic. Furthermore, FaaS workflows tend to be slow due to cascading cold starts, inter-function latency, and data download latency on the critical path. In this paper, we propose GeoFF, a serverless choreography middleware that executes FaaS workflows across different public and private FaaS platforms, including ad-hoc workflow recomposition. Furthermore, GeoFF supports function pre-warming and data pre-fetching. This minimizes end-to-end workflow latency by taking cold starts and data download latency off the critical path. In experiments with our proof-of-concept prototype and a realistic application, we were able to reduce end-to-end latency by more than 50%. △ Less

Submitted 23 October, 2025; v1 submitted 22 May, 2024; originally announced May 2024.

ProFaaStinate: Delaying Serverless Function Calls to Optimize Platform Performance

Authors: Trever Schirmer, Natalie Carl, Tobias Pfandzelter, David Bermbach

Abstract: Function-as-a-Service (FaaS) enables developers to run serverless applications without managing operational tasks. In current FaaS platforms, both synchronous and asynchronous calls are executed immediately. In this paper, we present ProFaaStinate, which extends serverless platforms to enable delayed execution of asynchronous function calls. This allows platforms to execute calls at convenient tim… ▽ More Function-as-a-Service (FaaS) enables developers to run serverless applications without managing operational tasks. In current FaaS platforms, both synchronous and asynchronous calls are executed immediately. In this paper, we present ProFaaStinate, which extends serverless platforms to enable delayed execution of asynchronous function calls. This allows platforms to execute calls at convenient times with higher resource availability or lower load. ProFaaStinate is able to optimize performance without requiring deep integration into the rest of the platform, or a complex systems model. In our evaluation, our prototype built on top of Nuclio can reduce request response latency and workflow duration while also preventing the system from being overloaded during load peaks. Using a document preparation use case, we show a 54% reduction in average request response latency. This reduction in resource usage benefits both platforms and users as cost savings. △ Less

Submitted 24 October, 2025; v1 submitted 27 September, 2023; originally announced September 2023.

Comments: Accepted for publication in Proc. of 9th International Workshop on Serverless Computing (WoSC 23)