The stakes could hardly be higher. Every video stream, industrial sensor reading, autonomous vehicle decision, and healthcare monitoring alert now traverses a layered computing infrastructure in which computation may happen in a hyperscale data center, a regional fog node, or a device at the very edge of the network. Task scheduling, the process of deciding which computing resource will execute which job and when, directly determines latency, throughput, cost, and energy consumption. Load balancing, its close companion, spreads work evenly across available resources to prevent bottlenecks and failures. When either process falters, the consequences ripple outward: service level agreements are violated, users experience lag, servers idle wastefully or overheat, and in safety-critical applications such as connected vehicles or remote surgery, delays can be dangerous. The survey emphasizes that quality of service, resource efficiency, and overall system performance all hinge on how well these two intertwined problems are solved.

What distinguishes this survey from its predecessors is its insistence on a unified, comparative lens. Earlier reviews, the authors note, frequently examined cloud, fog, and edge environments in isolation, obscuring the trade-offs that emerge when workloads migrate between layers. By contrast, the new analysis traces how the optimal scheduling strategy shifts with position in the continuum. In the cloud, where resources are abundant but network latency to end users is significant, meta-heuristic algorithms dominate the literature. These nature-inspired optimizers, including genetic algorithms, particle swarm optimization, ant colony optimization, artificial bee colony methods, grey wolf optimizers, whale optimization algorithms, and cuckoo search, iteratively explore vast search spaces to find near-optimal assignments of tasks to virtual machines. The survey catalogues their underlying mechanisms in detail, from the mutation and crossover operators borrowed from biological evolution to the physics-inspired strategies modeled on phenomena such as simulated annealing and gravitational search.

In fog and edge environments, the picture changes dramatically. Resources are scarce, geographically dispersed, and volatile; network conditions fluctuate; and decisions must often be made in milliseconds. Here, the survey finds, the literature increasingly leans on artificial intelligence and machine learning, particularly reinforcement learning, in which an agent learns a scheduling policy through trial-and-error interaction with its environment, and deep reinforcement learning, which uses deep neural networks to handle enormous state spaces that would overwhelm tabular methods. The reviewed studies span Q-learning approaches for energy-efficient cloud scheduling, deep Q-network variants with improved exploration strategies, multi-agent deep reinforcement learning for distributed fog systems, soft actor-critic methods for task offloading in the internet of vehicles, and meta-reinforcement learning techniques designed to adapt rapidly to unseen edge scenarios. Applications range from smart factories and smart cities to healthcare management systems, where prioritizing critical patients over routine workloads can be a matter of life and death.

The technical anatomy of these learning-based schedulers is one of the survey’s richest contributions. In a typical deep reinforcement learning formulation, the state captures the current load of servers, queue lengths, task characteristics, and network conditions; the action space represents possible task-to-resource assignments or offloading decisions; and the reward function encodes objectives such as minimized makespan, reduced energy consumption, lower latency, or fewer service level agreement violations. Because real deployments rarely optimize a single metric, multi-objective formulations have proliferated, often combining reinforcement learning with meta-heuristics in hybrid schemes. One reviewed study, for example, coupled an artificial bee colony algorithm with reinforcement learning to balance competing objectives in cloud environments, while others integrated fuzzy logic to handle the uncertainty inherent in fog-cloud workflow scheduling. The authors also document the role of federated reinforcement learning, which allows edge nodes to learn collaboratively without centralizing sensitive data, and long short-term memory networks used for proactive scheduling of streaming applications before demand spikes materialize.

Measuring success in this field is itself a subtle science, and the survey devotes substantial effort to standardizing the metrics by which scheduling algorithms should be judged. Its appendix enumerates formal definitions for a comprehensive battery of indicators: makespan, the completion time of the last task in a batch; throughput, the number of tasks completed per unit time; response time and turnaround time; resource utilization; degree of imbalance; energy consumption; monetary cost; migration time; reliability, defined as the ratio of successful executions to total executions; availability; and service level agreement violation, computed from host active time and performance degradation. By assembling these definitions in one place, the authors provide researchers with a common vocabulary, addressing a long-standing problem in which studies claiming improvements often measure incomparable quantities across incomparable testbeds.

That testbed problem receives its own treatment. The survey reviews the simulation ecosystems on which the field depends, from the venerable CloudSim and its extensions such as CloudSim Plus and CloudAnalyst, to iFogSim and FogNetSim++ for fog scenarios, PureEdgeSim for the full cloud-fog-edge spectrum, and GreenCloud, iCanCloud, DCSim, and SCORE for energy-aware data center modeling. The authors classify these tools by environment, features, implementation language, open-source status, and graphical interface, noting that reproducibility and cross-paradigm evaluation remain weak points. Many studies validate their algorithms only within a single simulator tuned to a single layer, making it difficult to know whether a scheduler that excels in a cloud testbed will survive contact with the unpredictable wireless links and device heterogeneity of a real edge deployment.

From this synthesis, the survey distills a set of critical findings and uncomfortable gaps. Performance trade-offs emerge everywhere: meta-heuristics can approach optimal solutions but may converge slowly or demand heavy computation; reinforcement learning agents adapt dynamically but require extensive training and can behave unpredictably under distribution shift. More fundamentally, the authors identify the lack of cross-layer scheduling metrics as a key deficiency, since no standard measure exists to evaluate a decision that spans cloud, fog, and edge simultaneously. They also flag the insufficient handling of dynamic network conditions, pointing out that many algorithms assume stable connectivity even as real-world edge systems contend with fading links, mobility, and congestion. The absence of unified benchmarks spanning the full continuum, and the scarcity of studies addressing security and privacy constraints in scheduling decisions, round out a research agenda that the authors lay out for the community.

The future directions the survey champions read like a blueprint for the next decade of distributed computing. AI-driven adaptive scheduling, in which schedulers continuously learn and re-learn as workloads and network conditions evolve, stands at the forefront, alongside energy-aware optimization that treats power consumption as a first-class objective rather than an afterthought. The authors envision deeper integration of meta-learning so that scheduling agents can generalize across environments, wider adoption of federated approaches that preserve data sovereignty at the edge, and hybrid architectures that combine the global search power of meta-heuristics with the real-time responsiveness of learned policies. As billions of devices join the internet of things and applications from autonomous transport to industrial automation demand guaranteed latency, the survey argues, the systems that manage computation must themselves become intelligent. This work, published as volume 29, article 738 of Cluster Computing, positions itself as a foundational resource for the researchers and practitioners who will build that intelligent infrastructure, offering them a single map of a field that has, until now, been scattered across three separate territories.

Subject of Research: Task scheduling and load balancing techniques across cloud, fog, and edge computing systems

Article Title: Task scheduling and load balancing in cloud, fog, and edge computing systems: a survey

Article References: Zorgati, R., Hamdi, H., & Omri, M. N. (2026). Task scheduling and load balancing in cloud, fog, and edge computing systems: a survey. Cluster Computing, 29(13), Article 738. https://doi.org/10.1007/s10586-026-06513-y

Image Credits: AI Generated

DOI: 10.1007/s10586-026-06513-y

Keywords: task scheduling, load balancing, cloud computing, fog computing, edge computing, reinforcement learning, deep reinforcement learning, metaheuristics, quality of service, energy optimization, internet of things, artificial intelligence