diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index 9accdf67d6..d053e81ca4 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -23,24 +23,21 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 )
 
-/*
- * This is a test memory database. Do not use for any production it does not get persisted
- */
-
-// MemDatabase imitates the key-value store levelDB for the test memory database.
+// MemDatabase is an in-memory key-value store.
 type MemDatabase struct {
 	db   map[string][]byte
 	lock sync.RWMutex
 }
 
-// NewMemDatabase inits a mock levelDB instance with a map.
+// NewMemDatabase creates an in-memory key-value store.
 func NewMemDatabase() *MemDatabase {
 	return &MemDatabase{
 		db: make(map[string][]byte),
 	}
 }
 
-// NewMemDatabaseWithCap inits a mock levelDB instance with a map and sets a maximum size..
+// NewMemDatabaseWithCap creates an in-memory key-value store with a specific
+// starting capacity item.
 func NewMemDatabaseWithCap(size int) *MemDatabase {
 	return &MemDatabase{
 		db: make(map[string][]byte, size),
@@ -64,7 +61,7 @@ func (db *MemDatabase) Has(key []byte) (bool, error) {
 	return ok, nil
 }
 
-// Get returns an error if the given key is not found.
+// Get retrieves the value associated with a given key.
 func (db *MemDatabase) Get(key []byte) ([]byte, error) {
 	db.lock.RLock()
 	defer db.lock.RUnlock()
@@ -75,7 +72,7 @@ func (db *MemDatabase) Get(key []byte) ([]byte, error) {
 	return nil, errors.New("not found")
 }
 
-// Keys returns a list of all keys in db.db.
+// Keys returns a list of all the keys present in the database.
 func (db *MemDatabase) Keys() [][]byte {
 	db.lock.RLock()
 	defer db.lock.RUnlock()
@@ -87,7 +84,7 @@ func (db *MemDatabase) Keys() [][]byte {
 	return keys
 }
 
-// Delete deletes the key from db.db.
+// Delete removes the specified entry from the database.
 func (db *MemDatabase) Delete(key []byte) error {
 	db.lock.Lock()
 	defer db.lock.Unlock()
@@ -96,15 +93,16 @@ func (db *MemDatabase) Delete(key []byte) error {
 	return nil
 }
 
-// Close performs no operation but imitates invocation of levelDB.Close().
+// Close implements the closer interface. For the memory database, this is a noop.
 func (db *MemDatabase) Close() {}
 
-// NewBatch sets memBatch.db equal to the receiver.
+// NewBatch creates a memory buffer to group together database writes and flush
+// them out in one go. Batches are not atomic, just an performance optimization.
 func (db *MemDatabase) NewBatch() Batch {
 	return &memBatch{db: db}
 }
 
-// Len returns the number of keys in db.db.
+// Len returns the number of entries in the database.
 func (db *MemDatabase) Len() int { return len(db.db) }
 
 type kv struct{ k, v []byte }