DEEPSEEK-V4.1 FLASH: PUSHING THE LIMITS OF KV CACHE COMPRESSION

Summary from the TLDR Dev newsletter

This deep dive explains how DeepSeek-V4.1 Flash combines a causal encoder-decoder, cross-layer sparse attention and index reuse, hierarchical retrieval, Engram memory, and FP4 storage to shrink the KV cache to 890 bytes per token. The 40-layer design activates 8B parameters during prefill and 16B during decoding, targeting lower HBM, SSD, and compute costs for long-horizon agent workloads.