diff --git a/db/c_level_db.go b/db/c_level_db.go
index e4450aaa..e867b000 100644
--- a/db/c_level_db.go
+++ b/db/c_level_db.go
@@ -22,8 +22,6 @@ type CLevelDB struct {
 	ro     *levigo.ReadOptions
 	wo     *levigo.WriteOptions
 	woSync *levigo.WriteOptions
-
-	cwwMutex
 }
 
 func NewCLevelDB(name string, dir string) (*CLevelDB, error) {
@@ -45,8 +43,6 @@ func NewCLevelDB(name string, dir string) (*CLevelDB, error) {
 		ro:     ro,
 		wo:     wo,
 		woSync: woSync,
-
-		cwwMutex: NewCWWMutex(),
 	}
 	return database, nil
 }
@@ -59,6 +55,10 @@ func (db *CLevelDB) Get(key []byte) []byte {
 	return res
 }
 
+func (db *CLevelDB) Has(key []byte) bool {
+	panic("not implemented yet")
+}
+
 func (db *CLevelDB) Set(key []byte, value []byte) {
 	err := db.db.Put(db.wo, key, value)
 	if err != nil {
@@ -99,9 +99,9 @@ func (db *CLevelDB) Close() {
 }
 
 func (db *CLevelDB) Print() {
-	itr := db.Iterator()
-	defer itr.Close()
-	for itr.Seek(nil); itr.Valid(); itr.Next() {
+	itr := db.Iterator(BeginningKey(), EndingKey())
+	defer itr.Release()
+	for ; itr.Valid(); itr.Next() {
 		key := itr.Key()
 		value := itr.Value()
 		fmt.Printf("[%X]:\t[%X]\n", key, value)
@@ -120,10 +120,6 @@ func (db *CLevelDB) Stats() map[string]string {
 	return stats
 }
 
-func (db *CLevelDB) CacheDB() CacheDB {
-	return NewCacheDB(db, db.GetWriteLockVersion())
-}
-
 //----------------------------------------
 // Batch
 
@@ -155,10 +151,19 @@ func (mBatch *cLevelDBBatch) Write() {
 //----------------------------------------
 // Iterator
 
-func (db *CLevelDB) Iterator() Iterator {
-	itr := db.db.NewIterator(db.ro)
-	itr.Seek([]byte{0x00})
-	return cLevelDBIterator{itr}
+func (db *CLevelDB) Iterator(start, end []byte) Iterator {
+	/*
+		XXX
+		itr := db.db.NewIterator(db.ro)
+		itr.Seek([]byte{0x00})
+		return cLevelDBIterator{itr}
+	*/
+	return nil
+}
+
+func (db *CLevelDB) ReverseIterator(start, end []byte) Iterator {
+	// XXX
+	return nil
 }
 
 type cLevelDBIterator struct {
@@ -204,7 +209,7 @@ func (c cLevelDBIterator) Prev() {
 	c.itr.Prev()
 }
 
-func (c cLevelDBIterator) Close() {
+func (c cLevelDBIterator) Release() {
 	c.itr.Close()
 }
 
diff --git a/db/cache_db.go b/db/cache_db.go
deleted file mode 100644
index 586f2f67..00000000
--- a/db/cache_db.go
+++ /dev/null
@@ -1,233 +0,0 @@
-/*
-package db
-
-import (
-	"fmt"
-	"sort"
-	"sync"
-	"sync/atomic"
-)
-
-// If value is nil but deleted is false,
-// it means the parent doesn't have the key.
-// (No need to delete upon Write())
-type cDBValue struct {
-	value   []byte
-	deleted bool
-	dirty   bool
-}
-
-// cacheDB wraps an in-memory cache around an underlying DB.
-type cacheDB struct {
-	mtx         sync.Mutex
-	cache       map[string]cDBValue
-	parent      DB
-	lockVersion interface{}
-
-	cwwMutex
-}
-
-// Needed by MultiStore.CacheWrap().
-var _ atomicSetDeleter = (*cacheDB)(nil)
-var _ CacheDB = (*cacheDB)(nil)
-
-// Users should typically not be required to call NewCacheDB directly, as the
-// DB implementations here provide a .CacheDB() function already.
-// `lockVersion` is typically provided by parent.GetWriteLockVersion().
-func NewCacheDB(parent DB, lockVersion interface{}) CacheDB {
-	db := &cacheDB{
-		cache:       make(map[string]cDBValue),
-		parent:      parent,
-		lockVersion: lockVersion,
-		cwwMutex:    NewCWWMutex(),
-	}
-	return db
-}
-
-func (db *cacheDB) Get(key []byte) []byte {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	dbValue, ok := db.cache[string(key)]
-	if !ok {
-		data := db.parent.Get(key)
-		dbValue = cDBValue{value: data, deleted: false, dirty: false}
-		db.cache[string(key)] = dbValue
-	}
-	return dbValue.value
-}
-
-func (db *cacheDB) Set(key []byte, value []byte) {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	db.SetNoLock(key, value)
-}
-
-func (db *cacheDB) SetSync(key []byte, value []byte) {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	db.SetNoLock(key, value)
-}
-
-func (db *cacheDB) SetNoLock(key []byte, value []byte) {
-	db.cache[string(key)] = cDBValue{value: value, deleted: false, dirty: true}
-}
-
-func (db *cacheDB) Delete(key []byte) {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	db.DeleteNoLock(key)
-}
-
-func (db *cacheDB) DeleteSync(key []byte) {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	db.DeleteNoLock(key)
-}
-
-func (db *cacheDB) DeleteNoLock(key []byte) {
-	db.cache[string(key)] = cDBValue{value: nil, deleted: true, dirty: true}
-}
-
-func (db *cacheDB) Close() {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	db.parent.Close()
-}
-
-func (db *cacheDB) Print() {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	fmt.Println("cacheDB\ncache:")
-	for key, value := range db.cache {
-		fmt.Printf("[%X]:\t[%v]\n", []byte(key), value)
-	}
-	fmt.Println("\nparent:")
-	db.parent.Print()
-}
-
-func (db *cacheDB) Stats() map[string]string {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	stats := make(map[string]string)
-	stats["cache.size"] = fmt.Sprintf("%d", len(db.cache))
-	stats["cache.lock_version"] = fmt.Sprintf("%v", db.lockVersion)
-	mergeStats(db.parent.Stats(), stats, "parent.")
-	return stats
-}
-
-func (db *cacheDB) Iterator() Iterator {
-	panic("cacheDB.Iterator() not yet supported")
-}
-
-func (db *cacheDB) NewBatch() Batch {
-	return &memBatch{db, nil}
-}
-
-// Implements `atomicSetDeleter` for Batch support.
-func (db *cacheDB) Mutex() *sync.Mutex {
-	return &(db.mtx)
-}
-
-// Write writes pending updates to the parent database and clears the cache.
-func (db *cacheDB) Write() {
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	// Optional sanity check to ensure that cacheDB is valid
-	if parent, ok := db.parent.(WriteLocker); ok {
-		if parent.TryWriteLock(db.lockVersion) {
-			// All good!
-		} else {
-			panic("cacheDB.Write() failed. Did this CacheDB expire?")
-		}
-	}
-
-	// We need a copy of all of the keys.
-	// Not the best, but probably not a bottleneck depending.
-	keys := make([]string, 0, len(db.cache))
-	for key, dbValue := range db.cache {
-		if dbValue.dirty {
-			keys = append(keys, key)
-		}
-	}
-	sort.Strings(keys)
-
-	batch := db.parent.NewBatch()
-	for _, key := range keys {
-		dbValue := db.cache[key]
-		if dbValue.deleted {
-			batch.Delete([]byte(key))
-		} else if dbValue.value == nil {
-			// Skip, it already doesn't exist in parent.
-		} else {
-			batch.Set([]byte(key), dbValue.value)
-		}
-	}
-	batch.Write()
-
-	// Clear the cache
-	db.cache = make(map[string]cDBValue)
-}
-
-//----------------------------------------
-// To cache-wrap this cacheDB further.
-
-func (db *cacheDB) CacheDB() CacheDB {
-	return NewCacheDB(db, db.GetWriteLockVersion())
-}
-
-// If the parent parent DB implements this, (e.g. such as a cacheDB parent to a
-// cacheDB child), cacheDB will call `parent.TryWriteLock()` before attempting
-// to write.
-type WriteLocker interface {
-	GetWriteLockVersion() (lockVersion interface{})
-	TryWriteLock(lockVersion interface{}) bool
-}
-
-// Implements TryWriteLocker.  Embed this in DB structs if desired.
-type cwwMutex struct {
-	mtx sync.Mutex
-	// CONTRACT: reading/writing to `*written` should use `atomic.*`.
-	// CONTRACT: replacing `written` with another *int32 should use `.mtx`.
-	written *int32
-}
-
-func NewCWWMutex() cwwMutex {
-	return cwwMutex{
-		written: new(int32),
-	}
-}
-
-func (cww *cwwMutex) GetWriteLockVersion() interface{} {
-	cww.mtx.Lock()
-	defer cww.mtx.Unlock()
-
-	// `written` works as a "version" object because it gets replaced upon
-	// successful TryWriteLock.
-	return cww.written
-}
-
-func (cww *cwwMutex) TryWriteLock(version interface{}) bool {
-	cww.mtx.Lock()
-	defer cww.mtx.Unlock()
-
-	if version != cww.written {
-		return false // wrong "WriteLockVersion"
-	}
-	if !atomic.CompareAndSwapInt32(cww.written, 0, 1) {
-		return false // already written
-	}
-
-	// New "WriteLockVersion"
-	cww.written = new(int32)
-	return true
-}
-*/
diff --git a/db/db.go b/db/db.go
index ba137743..7eec04d5 100644
--- a/db/db.go
+++ b/db/db.go
@@ -1,5 +1,7 @@
 package db
 
+import "fmt"
+
 //-----------------------------------------------------------------------------
 // Main entry
 
@@ -26,7 +28,7 @@ func registerDBCreator(backend string, creator dbCreator, force bool) {
 func NewDB(name string, backend string, dir string) DB {
 	db, err := backends[backend](name, dir)
 	if err != nil {
-		PanicSanity(Fmt("Error initializing DB: %v", err))
+		panic(fmt.Sprintf("Error initializing DB: %v", err))
 	}
 	return db
 }
diff --git a/db/fsdb.go b/db/fsdb.go
index 4b191445..b6e08daf 100644
--- a/db/fsdb.go
+++ b/db/fsdb.go
@@ -7,7 +7,6 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"sort"
 	"sync"
 
 	"github.com/pkg/errors"
@@ -29,8 +28,6 @@ func init() {
 type FSDB struct {
 	mtx sync.Mutex
 	dir string
-
-	cwwMutex
 }
 
 func NewFSDB(dir string) *FSDB {
@@ -39,8 +36,7 @@ func NewFSDB(dir string) *FSDB {
 		panic(errors.Wrap(err, "Creating FSDB dir "+dir))
 	}
 	database := &FSDB{
-		dir:      dir,
-		cwwMutex: NewCWWMutex(),
+		dir: dir,
 	}
 	return database
 }
@@ -59,6 +55,20 @@ func (db *FSDB) Get(key []byte) []byte {
 	return value
 }
 
+func (db *FSDB) Has(key []byte) bool {
+	db.mtx.Lock()
+	defer db.mtx.Unlock()
+
+	path := db.nameToPath(key)
+	_, err := read(path)
+	if os.IsNotExist(err) {
+		return false
+	} else if err != nil {
+		panic(errors.Wrap(err, fmt.Sprintf("Getting key %s (0x%X)", string(key), key)))
+	}
+	return true
+}
+
 func (db *FSDB) Set(key []byte, value []byte) {
 	db.mtx.Lock()
 	defer db.mtx.Unlock()
@@ -140,27 +150,32 @@ func (db *FSDB) Mutex() *sync.Mutex {
 	return &(db.mtx)
 }
 
-func (db *FSDB) CacheDB() CacheDB {
-	return NewCacheDB(db, db.GetWriteLockVersion())
+func (db *FSDB) Iterator(start, end []byte) Iterator {
+	/*
+		XXX
+		it := newMemDBIterator()
+		it.db = db
+		it.cur = 0
+
+		db.mtx.Lock()
+		defer db.mtx.Unlock()
+
+		// We need a copy of all of the keys.
+		// Not the best, but probably not a bottleneck depending.
+		keys, err := list(db.dir)
+		if err != nil {
+			panic(errors.Wrap(err, fmt.Sprintf("Listing keys in %s", db.dir)))
+		}
+		sort.Strings(keys)
+		it.keys = keys
+		return it
+	*/
+	return nil
 }
 
-func (db *FSDB) Iterator() Iterator {
-	it := newMemDBIterator()
-	it.db = db
-	it.cur = 0
-
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
-
-	// We need a copy of all of the keys.
-	// Not the best, but probably not a bottleneck depending.
-	keys, err := list(db.dir)
-	if err != nil {
-		panic(errors.Wrap(err, fmt.Sprintf("Listing keys in %s", db.dir)))
-	}
-	sort.Strings(keys)
-	it.keys = keys
-	return it
+func (db *FSDB) ReverseIterator(start, end []byte) Iterator {
+	// XXX
+	return nil
 }
 
 func (db *FSDB) nameToPath(name []byte) string {
diff --git a/db/go_level_db.go b/db/go_level_db.go
index cffe7329..e8ed99de 100644
--- a/db/go_level_db.go
+++ b/db/go_level_db.go
@@ -22,8 +22,6 @@ func init() {
 
 type GoLevelDB struct {
 	db *leveldb.DB
-
-	cwwMutex
 }
 
 func NewGoLevelDB(name string, dir string) (*GoLevelDB, error) {
@@ -33,8 +31,7 @@ func NewGoLevelDB(name string, dir string) (*GoLevelDB, error) {
 		return nil, err
 	}
 	database := &GoLevelDB{
-		db:       db,
-		cwwMutex: NewCWWMutex(),
+		db: db,
 	}
 	return database, nil
 }
@@ -51,6 +48,18 @@ func (db *GoLevelDB) Get(key []byte) []byte {
 	return res
 }
 
+func (db *GoLevelDB) Has(key []byte) bool {
+	_, err := db.db.Get(key, nil)
+	if err != nil {
+		if err == errors.ErrNotFound {
+			return false
+		} else {
+			PanicCrisis(err)
+		}
+	}
+	return true
+}
+
 func (db *GoLevelDB) Set(key []byte, value []byte) {
 	err := db.db.Put(key, value, nil)
 	if err != nil {
@@ -121,10 +130,6 @@ func (db *GoLevelDB) Stats() map[string]string {
 	return stats
 }
 
-func (db *GoLevelDB) CacheDB() CacheDB {
-	return NewCacheDB(db, db.GetWriteLockVersion())
-}
-
 //----------------------------------------
 // Batch
 
@@ -156,12 +161,21 @@ func (mBatch *goLevelDBBatch) Write() {
 //----------------------------------------
 // Iterator
 
-func (db *GoLevelDB) Iterator() Iterator {
-	itr := &goLevelDBIterator{
-		source: db.db.NewIterator(nil, nil),
-	}
-	itr.Seek(nil)
-	return itr
+func (db *GoLevelDB) Iterator(start, end []byte) Iterator {
+	/*
+		XXX
+		itr := &goLevelDBIterator{
+			source: db.db.NewIterator(nil, nil),
+		}
+		itr.Seek(nil)
+		return itr
+	*/
+	return nil
+}
+
+func (db *GoLevelDB) ReverseIterator(start, end []byte) Iterator {
+	// XXX
+	return nil
 }
 
 type goLevelDBIterator struct {
diff --git a/db/mem_db.go b/db/mem_db.go
index f5d55f3a..3127030a 100644
--- a/db/mem_db.go
+++ b/db/mem_db.go
@@ -3,7 +3,6 @@ package db
 import (
 	"bytes"
 	"fmt"
-	"sort"
 	"sync"
 )
 
@@ -16,14 +15,11 @@ func init() {
 type MemDB struct {
 	mtx sync.Mutex
 	db  map[string][]byte
-
-	cwwMutex
 }
 
 func NewMemDB() *MemDB {
 	database := &MemDB{
-		db:       make(map[string][]byte),
-		cwwMutex: NewCWWMutex(),
+		db: make(map[string][]byte),
 	}
 	return database
 }
@@ -35,6 +31,14 @@ func (db *MemDB) Get(key []byte) []byte {
 	return db.db[string(key)]
 }
 
+func (db *MemDB) Has(key []byte) bool {
+	db.mtx.Lock()
+	defer db.mtx.Unlock()
+
+	_, ok := db.db[string(key)]
+	return ok
+}
+
 func (db *MemDB) Set(key []byte, value []byte) {
 	db.mtx.Lock()
 	defer db.mtx.Unlock()
@@ -114,27 +118,32 @@ func (db *MemDB) Mutex() *sync.Mutex {
 	return &(db.mtx)
 }
 
-func (db *MemDB) CacheDB() CacheDB {
-	return NewCacheDB(db, db.GetWriteLockVersion())
-}
-
 //----------------------------------------
 
-func (db *MemDB) Iterator() Iterator {
-	it := newMemDBIterator()
-	it.db = db
-	it.cur = 0
+func (db *MemDB) Iterator(start, end []byte) Iterator {
+	/*
+		XXX
+		it := newMemDBIterator()
+		it.db = db
+		it.cur = 0
 
-	db.mtx.Lock()
-	defer db.mtx.Unlock()
+		db.mtx.Lock()
+		defer db.mtx.Unlock()
 
-	// We need a copy of all of the keys.
-	// Not the best, but probably not a bottleneck depending.
-	for key, _ := range db.db {
-		it.keys = append(it.keys, key)
-	}
-	sort.Strings(it.keys)
-	return it
+		// We need a copy of all of the keys.
+		// Not the best, but probably not a bottleneck depending.
+		for key, _ := range db.db {
+			it.keys = append(it.keys, key)
+		}
+		sort.Strings(it.keys)
+		return it
+	*/
+	return nil
+}
+
+func (db *MemDB) ReverseIterator(start, end []byte) Iterator {
+	// XXX
+	return nil
 }
 
 type memDBIterator struct {
diff --git a/db/types.go b/db/types.go
index f343e1d7..7422a515 100644
--- a/db/types.go
+++ b/db/types.go
@@ -54,12 +54,23 @@ type SetDeleter interface {
 
 //----------------------------------------
 
+func BeginningKey() []byte {
+	return []byte{}
+}
+
+func EndingKey() []byte {
+	return nil
+}
+
 /*
 	Usage:
 
-	for itr.Seek(mykey); itr.Valid(); itr.Next() {
+	var itr Iterator = ...
+	defer itr.Release()
+
+	for ; itr.Valid(); itr.Next() {
 		k, v := itr.Key(); itr.Value()
-		....
+		// ...
 	}
 */
 type Iterator interface {
@@ -106,6 +117,6 @@ type Iterator interface {
 	// This method is safe to call when Valid returns false.
 	GetError() error
 
-	// Close deallocates the given Iterator.
-	Close()
+	// Release deallocates the given Iterator.
+	Release()
 }
diff --git a/db/util.go b/db/util.go
index 5f381a5b..89c77762 100644
--- a/db/util.go
+++ b/db/util.go
@@ -1,82 +1,35 @@
 package db
 
-import "bytes"
-
-// A wrapper around itr that tries to keep the iterator
-// within the bounds as defined by `prefix`
-type prefixIterator struct {
-	itr     Iterator
-	prefix  []byte
-	invalid bool
-}
-
-func (pi *prefixIterator) Seek(key []byte) {
-	if !bytes.HasPrefix(key, pi.prefix) {
-		pi.invalid = true
-		return
-	}
-	pi.itr.Seek(key)
-	pi.checkInvalid()
-}
-
-func (pi *prefixIterator) checkInvalid() {
-	if !pi.itr.Valid() {
-		pi.invalid = true
-	}
-}
-
-func (pi *prefixIterator) Valid() bool {
-	if pi.invalid {
-		return false
-	}
-	key := pi.itr.Key()
-	ok := bytes.HasPrefix(key, pi.prefix)
-	if !ok {
-		pi.invalid = true
-		return false
-	}
-	return true
-}
-
-func (pi *prefixIterator) Next() {
-	if pi.invalid {
-		panic("prefixIterator Next() called when invalid")
-	}
-	pi.itr.Next()
-	pi.checkInvalid()
-}
-
-func (pi *prefixIterator) Prev() {
-	if pi.invalid {
-		panic("prefixIterator Prev() called when invalid")
-	}
-	pi.itr.Prev()
-	pi.checkInvalid()
-}
-
-func (pi *prefixIterator) Key() []byte {
-	if pi.invalid {
-		panic("prefixIterator Key() called when invalid")
-	}
-	return pi.itr.Key()
-}
-
-func (pi *prefixIterator) Value() []byte {
-	if pi.invalid {
-		panic("prefixIterator Value() called when invalid")
-	}
-	return pi.itr.Value()
-}
-
-func (pi *prefixIterator) Close()          { pi.itr.Close() }
-func (pi *prefixIterator) GetError() error { return pi.itr.GetError() }
-
 func IteratePrefix(db DB, prefix []byte) Iterator {
-	itr := db.Iterator()
-	pi := &prefixIterator{
-		itr:    itr,
-		prefix: prefix,
+	var start, end []byte
+	if len(prefix) == 0 {
+		start = BeginningKey()
+		end = EndingKey()
+	} else {
+		start = cp(prefix)
+		end = cpIncr(prefix)
 	}
-	pi.Seek(prefix)
-	return pi
+	return db.Iterator(start, end)
+}
+
+//----------------------------------------
+
+func cp(bz []byte) (ret []byte) {
+	ret = make([]byte, len(bz))
+	copy(ret, bz)
+	return ret
+}
+
+// CONTRACT: len(bz) > 0
+func cpIncr(bz []byte) (ret []byte) {
+	ret = cp(bz)
+	for i := len(bz) - 1; i >= 0; i-- {
+		if ret[i] < byte(0xFF) {
+			ret[i] += 1
+			return
+		} else {
+			ret[i] = byte(0x00)
+		}
+	}
+	return EndingKey()
 }