diff --git a/compress/decompress.go b/compress/decompress.go
index f4feb67c6..2c24c0394 100644
--- a/compress/decompress.go
+++ b/compress/decompress.go
@@ -116,6 +116,7 @@ type Getter struct {
 	mask        byte
 	uncovered   []int // Buffer for uncovered portions of the word
 	word        []byte
+	fName       string
 }
 
 func (g *Getter) zero() bool {
@@ -212,7 +213,7 @@ func (d *Decompressor) Count() int { return int(d.count) }
 // Getter is not thread-safe, but there can be multiple getters used simultaneously and concurrently
 // for the same decompressor
 func (d *Decompressor) MakeGetter() *Getter {
-	return &Getter{patternDict: &d.dict, posDict: &d.posDict, data: d.data[d.wordsStart:], uncovered: make([]int, 0, 128)}
+	return &Getter{patternDict: &d.dict, posDict: &d.posDict, data: d.data[d.wordsStart:], uncovered: make([]int, 0, 128), fName: d.compressedFile}
 }
 
 func (g *Getter) Reset(offset uint64) {
@@ -247,7 +248,7 @@ func (g *Getter) Next(buf []byte) ([]byte, uint64) {
 		lastPos = intPos
 		pattern := g.nextPattern()
 		if len(g.word) < intPos {
-			panic("likely .idx is invalid")
+			panic(fmt.Sprintf("likely .idx is invalid: %s", g.fName))
 		}
 		copy(g.word[intPos:], pattern)
 		if intPos > lastUncovered {
@@ -284,7 +285,7 @@ func (g *Getter) Skip() uint64 {
 		intPos := lastPos + int(pos) - 1
 		lastPos = intPos
 		if wordLen < intPos {
-			panic("likely .idx is invalid")
+			panic(fmt.Sprintf("likely .idx is invalid: %s", g.fName))
 		}
 		if intPos > lastUncovered {
 			add += uint64(intPos - lastUncovered)
@@ -402,7 +403,7 @@ func (g *Getter) MatchPrefix(buf []byte) bool {
 		intPos := lastPos + int(pos) - 1
 		lastPos = intPos
 		if wordLen < intPos {
-			panic("likely .idx is invalid")
+			panic(fmt.Sprintf("likely .idx is invalid: %s", g.fName))
 		}
 		pattern = g.nextPattern()
 		if strings.HasPrefix(string(pattern), string(buf)) {
diff --git a/etl/dataprovider.go b/etl/dataprovider.go
index 03dd782fc..237a3a32b 100644
--- a/etl/dataprovider.go
+++ b/etl/dataprovider.go
@@ -110,10 +110,11 @@ func (p *fileDataProvider) String() string {
 }
 
 func writeToDisk(encoder Encoder, entries []sortableBufferEntry) error {
-	pair := [2][]byte{}
+	pair := make([][]byte, 2)
+	pairInterface := interface{}(pair) // to avoid interface cast on each iteration
 	for i := range entries {
 		pair[0], pair[1] = entries[i].key, entries[i].value
-		if err := encoder.Encode(pair); err != nil {
+		if err := encoder.Encode(pairInterface); err != nil {
 			return fmt.Errorf("error writing entries to disk: %w", err)
 		}
 	}
diff --git a/recsplit/recsplit.go b/recsplit/recsplit.go
index f9e24487f..8f6cd0ec9 100644
--- a/recsplit/recsplit.go
+++ b/recsplit/recsplit.go
@@ -24,9 +24,7 @@ import (
 	"math"
 	"math/bits"
 	"os"
-	"path/filepath"
 
-	"github.com/ledgerwatch/erigon-lib/common"
 	"github.com/ledgerwatch/erigon-lib/etl"
 	"github.com/ledgerwatch/erigon-lib/recsplit/eliasfano16"
 	"github.com/ledgerwatch/erigon-lib/recsplit/eliasfano32"
@@ -97,6 +95,7 @@ type RecSplit struct {
 	indexW             *bufio.Writer
 	bytesPerRec        int
 	numBuf             [8]byte
+	bucketKeyBuf       [16]byte
 	trace              bool
 	prevOffset         uint64 // Previously added offset (for calculating minDelta for Elias Fano encoding of "enum -> offset" index)
 	minDelta           uint64 // minDelta for Elias Fano encoding of "enum -> offset" index
@@ -281,11 +280,9 @@ func (rs *RecSplit) AddKey(key []byte, offset uint64) error {
 	rs.hasher.Reset()
 	rs.hasher.Write(key) //nolint:errcheck
 	hi, lo := rs.hasher.Sum128()
-	var bucketKey [16]byte
-	binary.BigEndian.PutUint64(bucketKey[:], remap(hi, rs.bucketCount))
-	binary.BigEndian.PutUint64(bucketKey[8:], lo)
-	var offsetVal [8]byte
-	binary.BigEndian.PutUint64(offsetVal[:], offset)
+	binary.BigEndian.PutUint64(rs.bucketKeyBuf[:], remap(hi, rs.bucketCount))
+	binary.BigEndian.PutUint64(rs.bucketKeyBuf[8:], lo)
+	binary.BigEndian.PutUint64(rs.numBuf[:], offset)
 	if offset > rs.maxOffset {
 		rs.maxOffset = offset
 	}
@@ -297,16 +294,15 @@ func (rs *RecSplit) AddKey(key []byte, offset uint64) error {
 	}
 
 	if rs.enums {
-		if err := rs.offsetCollector.Collect(offsetVal[:], nil); err != nil {
+		if err := rs.offsetCollector.Collect(rs.numBuf[:], nil); err != nil {
 			return err
 		}
-		var keyIdx [8]byte
-		binary.BigEndian.PutUint64(keyIdx[:], rs.keysAdded)
-		if err := rs.bucketCollector.Collect(bucketKey[:], keyIdx[:]); err != nil {
+		binary.BigEndian.PutUint64(rs.numBuf[:], rs.keysAdded)
+		if err := rs.bucketCollector.Collect(rs.bucketKeyBuf[:], rs.numBuf[:]); err != nil {
 			return err
 		}
 	} else {
-		if err := rs.bucketCollector.Collect(bucketKey[:], offsetVal[:]); err != nil {
+		if err := rs.bucketCollector.Collect(rs.bucketKeyBuf[:], rs.numBuf[:]); err != nil {
 			return err
 		}
 	}
@@ -495,9 +491,7 @@ func (rs *RecSplit) loadFuncOffset(k, _ []byte, _ etl.CurrentTableReader, _ etl.
 // Build has to be called after all the keys have been added, and it initiates the process
 // of building the perfect hash function and writing index into a file
 func (rs *RecSplit) Build() error {
-	_, fileName := filepath.Split(rs.indexFile)
-	tmpIdxFilePath := filepath.Join(rs.tmpDir, fileName)
-	common.MustExist(rs.tmpDir)
+	tmpIdxFilePath := rs.indexFile + ".tmp"
 
 	if rs.built {
 		return fmt.Errorf("already built")
@@ -622,8 +616,6 @@ func (rs *RecSplit) Build() error {
 	_ = rs.indexW.Flush()
 	_ = rs.indexF.Sync()
 	_ = rs.indexF.Close()
-	dir, _ := filepath.Split(rs.indexFile)
-	common.MustExist(dir)
 	if err := os.Rename(tmpIdxFilePath, rs.indexFile); err != nil {
 		return err
 	}