Federated Learning Under Temporal Drift -- Mitigating Catastrophic Forgetting via Experience Replay

Sahasra Kokkula; Daniel David; Aaditya Baruah

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arXiv · 2601.13456

Federated Learning Under Temporal Drift -- Mitigating Catastrophic Forgetting via Experience Replay

Sahasra Kokkula·Daniel David·Aaditya Baruah

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Abstract

Federated Learning struggles under temporal concept drift where client data distributions shift over time. We demonstrate that standard FedAvg suffers catastrophic forgetting under seasonal drift on Fashion-MNIST, with accuracy dropping from 74% to 28%. We propose client-side experience replay, where each client maintains a small buffer of past samples mixed with current data during local training. This simple approach requires no changes to server aggregation. Experiments show that a 50-sample-per-class buffer restores performance to 78-82%, effectively preventing forgetting. Our ablation study reveals a clear memory-accuracy trade-off as buffer size increases.

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Sahasra Kokkula, Daniel David, Aaditya Baruah. 2026-01-19. Federated Learning Under Temporal Drift -- Mitigating Catastrophic Forgetting via Experience Replay. https://arxiv.org/abs/2601.13456

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