@inproceedings{dwivedi-etal-2026-efficient,
title = "Efficient Multi-Tenant {L}o{RA} Serving for Encoder Models via Late-Fusion Batched Matrix Multiplication",
author = "Dwivedi, Ashutosh Rupoliya and
Shrikant, Keshav and
Rupaliya, Jyotsna",
editor = "Atanasova, Pepa and
Haffari, Gholamreza and
Wang, Minghan",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-industry.224/",
pages = "3753--3763",
ISBN = "979-8-89176-460-6",
abstract = "Low-Rank Adaptation (LoRA) has become a popular method to adapt pre-trained models to specific domains. Applied to encoders in a multi-tenant service, it lets each tenant specialize a shared model for classification, retrieval, or ranking. Existing multi-tenant LoRA serving systems target autoregressive decoders, and for encoders the available tooling supports only per-request adapter swapping, whose cost grows with the number of registered adapters. We observe that, unlike decoder generation, the encoder forward pass is compute-bound and dominated by the shared base projections, so per-tenant adaptation can be expressed as plain batched matrix multiplication with no custom kernels. We present LateFuse, a pure-PyTorch system that serves many different LoRA-adapted encoders in a single shared forward pass on one GPU. LateFuse fuses adapters late, in activation space: the base projections run once over the mixed-tenant batch, while per-sample low-rank deltas and per-tenant classification heads are applied as batched matrix multiplications. Tenant weights are never merged into the shared base, ruling out cross-tenant contamination by construction. Our evaluation shows that LateFuse serving latency stays flat as the adapter pool grows to tens of thousands on a single GPU, and that it achieves 5.6{--}21.2x higher throughput than HuggingFace PEFT{'}s native mixed-batch API and up to 521{\texttimes} over per-adapter swapping, while registering new adapters over 299x faster."
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<abstract>Low-Rank Adaptation (LoRA) has become a popular method to adapt pre-trained models to specific domains. Applied to encoders in a multi-tenant service, it lets each tenant specialize a shared model for classification, retrieval, or ranking. Existing multi-tenant LoRA serving systems target autoregressive decoders, and for encoders the available tooling supports only per-request adapter swapping, whose cost grows with the number of registered adapters. We observe that, unlike decoder generation, the encoder forward pass is compute-bound and dominated by the shared base projections, so per-tenant adaptation can be expressed as plain batched matrix multiplication with no custom kernels. We present LateFuse, a pure-PyTorch system that serves many different LoRA-adapted encoders in a single shared forward pass on one GPU. LateFuse fuses adapters late, in activation space: the base projections run once over the mixed-tenant batch, while per-sample low-rank deltas and per-tenant classification heads are applied as batched matrix multiplications. Tenant weights are never merged into the shared base, ruling out cross-tenant contamination by construction. Our evaluation shows that LateFuse serving latency stays flat as the adapter pool grows to tens of thousands on a single GPU, and that it achieves 5.6–21.2x higher throughput than HuggingFace PEFT’s native mixed-batch API and up to 521× over per-adapter swapping, while registering new adapters over 299x faster.</abstract>
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%0 Conference Proceedings
%T Efficient Multi-Tenant LoRA Serving for Encoder Models via Late-Fusion Batched Matrix Multiplication
%A Dwivedi, Ashutosh Rupoliya
%A Shrikant, Keshav
%A Rupaliya, Jyotsna
%Y Atanasova, Pepa
%Y Haffari, Gholamreza
%Y Wang, Minghan
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-460-6
%F dwivedi-etal-2026-efficient
%X Low-Rank Adaptation (LoRA) has become a popular method to adapt pre-trained models to specific domains. Applied to encoders in a multi-tenant service, it lets each tenant specialize a shared model for classification, retrieval, or ranking. Existing multi-tenant LoRA serving systems target autoregressive decoders, and for encoders the available tooling supports only per-request adapter swapping, whose cost grows with the number of registered adapters. We observe that, unlike decoder generation, the encoder forward pass is compute-bound and dominated by the shared base projections, so per-tenant adaptation can be expressed as plain batched matrix multiplication with no custom kernels. We present LateFuse, a pure-PyTorch system that serves many different LoRA-adapted encoders in a single shared forward pass on one GPU. LateFuse fuses adapters late, in activation space: the base projections run once over the mixed-tenant batch, while per-sample low-rank deltas and per-tenant classification heads are applied as batched matrix multiplications. Tenant weights are never merged into the shared base, ruling out cross-tenant contamination by construction. Our evaluation shows that LateFuse serving latency stays flat as the adapter pool grows to tens of thousands on a single GPU, and that it achieves 5.6–21.2x higher throughput than HuggingFace PEFT’s native mixed-batch API and up to 521× over per-adapter swapping, while registering new adapters over 299x faster.
%U https://aclanthology.org/2026.emnlp-industry.224/
%P 3753-3763
Markdown (Informal)
[Efficient Multi-Tenant LoRA Serving for Encoder Models via Late-Fusion Batched Matrix Multiplication](https://aclanthology.org/2026.emnlp-industry.224/) (Dwivedi et al., EMNLP 2026)
ACL