diff --git a/arc_cache_test.go b/arc_cache_test.go
index a15ff2d..64f45df 100644
--- a/arc_cache_test.go
+++ b/arc_cache_test.go
@@ -2,7 +2,11 @@ package blockstore
 
 import (
 	"context"
+	"io"
+	"math/rand"
+	"sync/atomic"
 	"testing"
+	"time"
 
 	blocks "github.com/ipfs/go-block-format"
 	cid "github.com/ipfs/go-cid"
@@ -26,7 +30,7 @@ func testArcCached(ctx context.Context, bs Blockstore) (*arccache, error) {
 	return nil, err
 }
 
-func createStores(t *testing.T) (*arccache, Blockstore, *callbackDatastore) {
+func createStores(t testing.TB) (*arccache, Blockstore, *callbackDatastore) {
 	cd := &callbackDatastore{f: func() {}, ds: ds.NewMapDatastore()}
 	bs := NewBlockstore(syncds.MutexWrap(cd))
 	arc, err := testArcCached(context.TODO(), bs)
@@ -275,5 +279,120 @@ func TestPutManyCaches(t *testing.T) {
 		trap("PunMany has hit datastore", cd, t)
 		arc.PutMany([]blocks.Block{exampleBlock})
 	})
+}
+
+func BenchmarkARCCacheConcurrentOps(b *testing.B) {
+	// ~4k blocks seems high enough to be realistic,
+	// but low enough to cause collisions.
+	// Keep it as a power of 2, to simplify code below.
+	const numBlocks = 4 << 10
+
+	dummyBlocks := make([]blocks.Block, numBlocks)
+
+	{
+		// scope dummyRand to prevent its unsafe concurrent use below
+		dummyRand := rand.New(rand.NewSource(time.Now().UnixNano()))
+		for i := range dummyBlocks {
+			dummy := make([]byte, 32)
+			if _, err := io.ReadFull(dummyRand, dummy); err != nil {
+				b.Fatal(err)
+			}
+			dummyBlocks[i] = blocks.NewBlock(dummy)
+		}
+	}
+
+	// Each test begins with half the blocks present in the cache.
+	// This allows test cases to have both hits and misses,
+	// regardless of whether or not they do Puts.
+	putHalfBlocks := func(arc *arccache) {
+		for i, block := range dummyBlocks {
+			if i%2 == 0 {
+				if err := arc.Put(block); err != nil {
+					b.Fatal(err)
+				}
+			}
+		}
+	}
+
+	// We always mix just two operations at a time.
+	const numOps = 2
+	var testOps = []struct {
+		name string
+		ops  [numOps]func(*arccache, blocks.Block)
+	}{
+		{"PutDelete", [...]func(*arccache, blocks.Block){
+			func(arc *arccache, block blocks.Block) {
+				arc.Put(block)
+			},
+			func(arc *arccache, block blocks.Block) {
+				arc.DeleteBlock(block.Cid())
+			},
+		}},
+		{"GetDelete", [...]func(*arccache, blocks.Block){
+			func(arc *arccache, block blocks.Block) {
+				arc.Get(block.Cid())
+			},
+			func(arc *arccache, block blocks.Block) {
+				arc.DeleteBlock(block.Cid())
+			},
+		}},
+		{"GetPut", [...]func(*arccache, blocks.Block){
+			func(arc *arccache, block blocks.Block) {
+				arc.Get(block.Cid())
+			},
+			func(arc *arccache, block blocks.Block) {
+				arc.Put(block)
+			},
+		}},
+	}
 
+	for _, test := range testOps {
+		test := test // prevent reuse of the range var
+		b.Run(test.name, func(b *testing.B) {
+			arc, _, _ := createStores(b)
+			putHalfBlocks(arc)
+			var opCounts [numOps]uint64
+
+			b.ResetTimer()
+			b.ReportAllocs()
+
+			b.RunParallel(func(pb *testing.PB) {
+				rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
+				for pb.Next() {
+					n := rnd.Int63()
+					blockIdx := n % numBlocks         // lower bits decide the block
+					opIdx := (n / numBlocks) % numOps // higher bits decide what operation
+
+					block := dummyBlocks[blockIdx]
+					op := test.ops[opIdx]
+					op(arc, block)
+
+					atomic.AddUint64(&opCounts[opIdx], 1)
+				}
+			})
+
+			// We expect each op to fire roughly an equal amount of times.
+			// Error otherwise, as that likely means the logic is wrong.
+			var minIdx, maxIdx int
+			var minCount, maxCount uint64
+			for opIdx, count := range opCounts {
+				if minCount == 0 || count < minCount {
+					minIdx = opIdx
+					minCount = count
+				}
+				if maxCount == 0 || count > maxCount {
+					maxIdx = opIdx
+					maxCount = count
+				}
+			}
+			// Skip this check if we ran few times, to avoid false positives.
+			if maxCount > 100 {
+				ratio := float64(maxCount) / float64(minCount)
+				if maxRatio := 2.0; ratio > maxRatio {
+					b.Fatalf("op %d ran %fx as many times as %d", maxIdx, ratio, minIdx)
+				}
+			}
+
+		})
+	}
 }
diff --git a/go.sum b/go.sum
index cc30010..6dcd339 100644
--- a/go.sum
+++ b/go.sum
@@ -1,4 +1,3 @@
-github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -12,11 +11,9 @@ github.com/ipfs/bbloom v0.0.4 h1:Gi+8EGJ2y5qiD5FbsbpX/TMNcJw8gSqr7eyjHa4Fhvs=
 github.com/ipfs/bbloom v0.0.4/go.mod h1:cS9YprKXpoZ9lT0n/Mw/a6/aFV6DTjTLYHeA+gyqMG0=
 github.com/ipfs/go-block-format v0.0.3 h1:r8t66QstRp/pd/or4dpnbVfXT5Gt7lOqRvC+/dDTpMc=
 github.com/ipfs/go-block-format v0.0.3/go.mod h1:4LmD4ZUw0mhO+JSKdpWwrzATiEfM7WWgQ8H5l6P8MVk=
-github.com/ipfs/go-cid v0.0.5 h1:o0Ix8e/ql7Zb5UVUJEUfjsWCIY8t48++9lR8qi6oiJU=
 github.com/ipfs/go-cid v0.0.5/go.mod h1:plgt+Y5MnOey4vO4UlUazGqdbEXuFYitED67FexhXog=
 github.com/ipfs/go-cid v0.0.7 h1:ysQJVJA3fNDF1qigJbsSQOdjhVLsOEoPdh0+R97k3jY=
 github.com/ipfs/go-cid v0.0.7/go.mod h1:6Ux9z5e+HpkQdckYoX1PG/6xqKspzlEIR5SDmgqgC/I=
-github.com/ipfs/go-datastore v0.4.1 h1:W4ZfzyhNi3xmuU5dQhjfuRn/wFuqEE1KnOmmQiOevEY=
 github.com/ipfs/go-datastore v0.4.1/go.mod h1:SX/xMIKoCszPqp+z9JhPYCmoOoXTvaa13XEbGtsFUhA=
 github.com/ipfs/go-datastore v0.4.2 h1:h8/n7WPzhp239kkLws+epN3Ic7YtcBPgcaXfEfdVDWM=
 github.com/ipfs/go-datastore v0.4.2/go.mod h1:SX/xMIKoCszPqp+z9JhPYCmoOoXTvaa13XEbGtsFUhA=
@@ -46,7 +43,6 @@ github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1 h1:lYpkrQH5ajf0
 github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1/go.mod h1:pD8RvIylQ358TN4wwqatJ8rNavkEINozVn9DtGI3dfQ=
 github.com/minio/sha256-simd v0.1.1-0.20190913151208-6de447530771 h1:MHkK1uRtFbVqvAgvWxafZe54+5uBxLluGylDiKgdhwo=
 github.com/minio/sha256-simd v0.1.1-0.20190913151208-6de447530771/go.mod h1:B5e1o+1/KgNmWrSQK08Y6Z1Vb5pwIktudl0J58iy0KM=
-github.com/mr-tron/base58 v1.1.0 h1:Y51FGVJ91WBqCEabAi5OPUz38eAx8DakuAm5svLcsfQ=
 github.com/mr-tron/base58 v1.1.0/go.mod h1:xcD2VGqlgYjBdcBLw+TuYLr8afG+Hj8g2eTVqeSzSU8=
 github.com/mr-tron/base58 v1.1.3 h1:v+sk57XuaCKGXpWtVBX8YJzO7hMGx4Aajh4TQbdEFdc=
 github.com/mr-tron/base58 v1.1.3/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
@@ -54,11 +50,9 @@ github.com/multiformats/go-base32 v0.0.3 h1:tw5+NhuwaOjJCC5Pp82QuXbrmLzWg7uxlMFp
 github.com/multiformats/go-base32 v0.0.3/go.mod h1:pLiuGC8y0QR3Ue4Zug5UzK9LjgbkL8NSQj0zQ5Nz/AA=
 github.com/multiformats/go-base36 v0.1.0 h1:JR6TyF7JjGd3m6FbLU2cOxhC0Li8z8dLNGQ89tUg4F4=
 github.com/multiformats/go-base36 v0.1.0/go.mod h1:kFGE83c6s80PklsHO9sRn2NCoffoRdUUOENyW/Vv6sM=
-github.com/multiformats/go-multibase v0.0.1 h1:PN9/v21eLywrFWdFNsFKaU04kLJzuYzmrJR+ubhT9qA=
 github.com/multiformats/go-multibase v0.0.1/go.mod h1:bja2MqRZ3ggyXtZSEDKpl0uO/gviWFaSteVbWT51qgs=
 github.com/multiformats/go-multibase v0.0.3 h1:l/B6bJDQjvQ5G52jw4QGSYeOTZoAwIO77RblWplfIqk=
 github.com/multiformats/go-multibase v0.0.3/go.mod h1:5+1R4eQrT3PkYZ24C3W2Ue2tPwIdYQD509ZjSb5y9Oc=
-github.com/multiformats/go-multihash v0.0.13 h1:06x+mk/zj1FoMsgNejLpy6QTvJqlSt/BhLEy87zidlc=
 github.com/multiformats/go-multihash v0.0.13/go.mod h1:VdAWLKTwram9oKAatUcLxBNUjdtcVwxObEQBtRfuyjc=
 github.com/multiformats/go-multihash v0.0.14 h1:QoBceQYQQtNUuf6s7wHxnE2c8bhbMqhfGzNI032se/I=
 github.com/multiformats/go-multihash v0.0.14/go.mod h1:VdAWLKTwram9oKAatUcLxBNUjdtcVwxObEQBtRfuyjc=
@@ -82,16 +76,13 @@ golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8 h1:1wopBVtVdWnn03fZelqdXT
 golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de h1:5hukYrvBGR8/eNkX5mdUezrA6JiaEZDtJb9Ei+1LlBs=
 golang.org/x/lint v0.0.0-20190930215403-16217165b5de/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
-golang.org/x/net v0.0.0-20190227160552-c95aed5357e7 h1:C2F/nMkR/9sfUTpvR3QrjBuTdvMUC/cFajkphs1YLQo=
 golang.org/x/net v0.0.0-20190227160552-c95aed5357e7/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3 h1:0GoQqolDA55aaLxZyTzK/Y2ePZzZTUrRacwib7cNsYQ=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859 h1:R/3boaszxrf1GEUWTVDzSKVwLmSJpwZ1yqXm8j0v2QI=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223 h1:DH4skfRX4EBpamg7iV4ZlCpblAHI6s6TDM39bFZumv8=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=