An optimized document-indexing device is based on a pruned inverted index structure mapped to hardware. The device can be accommodated on a single chip and can be reprogrammed to accommodate index structures of different lengths and support varied posting-list sizes and varied term list sizes, thus sustaining high reusability and efficiency for a single device. The device can be used either as an internal slave component or as an external co-processor. The device controllers are efficient in resource demands and take only a minimal percentage of the logic and memory space of the hardware device.