diff --git a/fdbclient/DatabaseConfiguration.cpp b/fdbclient/DatabaseConfiguration.cpp
index cef31d134e..3328443fc7 100644
--- a/fdbclient/DatabaseConfiguration.cpp
+++ b/fdbclient/DatabaseConfiguration.cpp
@@ -20,6 +20,9 @@
 
 #include "fdbclient/DatabaseConfiguration.h"
 #include "fdbclient/SystemData.h"
+#include "flow/ITrace.h"
+#include "flow/Trace.h"
+#include "flow/genericactors.actor.h"
 
 DatabaseConfiguration::DatabaseConfiguration() {
 	resetInternal();
@@ -49,6 +52,10 @@ void DatabaseConfiguration::resetInternal() {
 	storageMigrationType = StorageMigrationType::DEFAULT;
 }
 
+int toInt(ValueRef const& v) {
+	return atoi(v.toString().c_str());
+}
+
 void parse(int* i, ValueRef const& v) {
 	// FIXME: Sanity checking
 	*i = atoi(v.toString().c_str());
@@ -466,6 +473,64 @@ std::string DatabaseConfiguration::toString() const {
 	return json_spirit::write_string(json_spirit::mValue(toJSON()), json_spirit::Output_options::none);
 }
 
+Key getKeyWithPrefix(std::string const& k) {
+	return StringRef(k).withPrefix(configKeysPrefix);
+}
+
+void DatabaseConfiguration::overwriteProxiesCount() {
+	Key commitProxiesKey = getKeyWithPrefix("commit_proxies");
+	Key grvProxiesKey = getKeyWithPrefix("grv_proxies");
+	Key proxiesKey = getKeyWithPrefix("proxies");
+	Optional<ValueRef> optCommitProxies = DatabaseConfiguration::get(commitProxiesKey);
+	Optional<ValueRef> optGrvProxies = DatabaseConfiguration::get(grvProxiesKey);
+	Optional<ValueRef> optProxies = DatabaseConfiguration::get(proxiesKey);
+
+	const int mutableGrvProxyCount = optGrvProxies.present() ? toInt(optGrvProxies.get()) : 0;
+	const int mutableCommitProxyCount = optCommitProxies.present() ? toInt(optCommitProxies.get()) : 0;
+	const int mutableProxiesCount = optProxies.present() ? toInt(optProxies.get()) : 0;
+
+	if (mutableProxiesCount > 1) {
+		TraceEvent(SevDebug, "OverwriteProxiesCount")
+		    .detail("CPCount", commitProxyCount)
+		    .detail("MutableCPCount", mutableCommitProxyCount)
+		    .detail("GrvCount", grvProxyCount)
+		    .detail("MutableGrvCPCount", mutableGrvProxyCount)
+		    .detail("MutableProxiesCount", mutableProxiesCount);
+
+		if (grvProxyCount == -1 && commitProxyCount > 0) {
+			if (mutableProxiesCount > commitProxyCount) {
+				grvProxyCount = mutableProxiesCount - commitProxyCount;
+			} else {
+				// invalid configuration; provision min GrvProxies
+				grvProxyCount = 1;
+				commitProxyCount = mutableProxiesCount - 1;
+			}
+		} else if (grvProxyCount > 0 && commitProxyCount == -1) {
+			if (mutableProxiesCount > grvProxyCount) {
+				commitProxyCount = mutableProxiesCount - grvProxyCount;
+			} else {
+				// invalid configuration; provision min CommitProxies
+				commitProxyCount = 1;
+				grvProxyCount = mutableProxiesCount - 1;
+			}
+		} else if (grvProxyCount == -1 && commitProxyCount == -1) {
+			// Use DEFAULT_COMMIT_GRV_PROXIES_RATIO to split proxies between Grv & Commit proxies
+			const int derivedGrvProxyCount =
+			    std::max(1,
+			             std::min(CLIENT_KNOBS->DEFAULT_MAX_GRV_PROXIES,
+			                      mutableProxiesCount / (CLIENT_KNOBS->DEFAULT_COMMIT_GRV_PROXIES_RATIO + 1)));
+
+			grvProxyCount = derivedGrvProxyCount;
+			commitProxyCount = mutableProxiesCount - grvProxyCount;
+		}
+
+		TraceEvent(SevDebug, "OverwriteProxiesCountResult")
+		    .detail("CommitProxyCount", commitProxyCount)
+		    .detail("GrvProxyCount", grvProxyCount)
+		    .detail("ProxyCount", mutableProxiesCount);
+	}
+}
+
 bool DatabaseConfiguration::setInternal(KeyRef key, ValueRef value) {
 	KeyRef ck = key.removePrefix(configKeysPrefix);
 	int type;
@@ -473,9 +538,13 @@ bool DatabaseConfiguration::setInternal(KeyRef key, ValueRef value) {
 	if (ck == LiteralStringRef("initialized")) {
 		initialized = true;
 	} else if (ck == LiteralStringRef("commit_proxies")) {
-		parse(&commitProxyCount, value);
+		commitProxyCount = toInt(value);
+		if (commitProxyCount == -1)
+			overwriteProxiesCount();
 	} else if (ck == LiteralStringRef("grv_proxies")) {
-		parse(&grvProxyCount, value);
+		grvProxyCount = toInt(value);
+		if (grvProxyCount == -1)
+			overwriteProxiesCount();
 	} else if (ck == LiteralStringRef("resolvers")) {
 		parse(&resolverCount, value);
 	} else if (ck == LiteralStringRef("logs")) {
@@ -557,21 +626,7 @@ bool DatabaseConfiguration::setInternal(KeyRef key, ValueRef value) {
 		parse((&type), value);
 		storageMigrationType = (StorageMigrationType::MigrationType)type;
 	} else if (ck == LiteralStringRef("proxies")) {
-		int proxiesCount;
-		parse(&proxiesCount, value);
-		if (proxiesCount > 1) {
-			int derivedGrvProxyCount =
-			    std::max(1,
-			             std::min(CLIENT_KNOBS->DEFAULT_MAX_GRV_PROXIES,
-			                      proxiesCount / (CLIENT_KNOBS->DEFAULT_COMMIT_GRV_PROXIES_RATIO + 1)));
-			int derivedCommitProxyCount = proxiesCount - derivedGrvProxyCount;
-			if (grvProxyCount == -1) {
-				grvProxyCount = derivedGrvProxyCount;
-			}
-			if (commitProxyCount == -1) {
-				commitProxyCount = derivedCommitProxyCount;
-			}
-		}
+		overwriteProxiesCount();
 	} else {
 		return false;
 	}
diff --git a/fdbclient/DatabaseConfiguration.h b/fdbclient/DatabaseConfiguration.h
index a390907529..81bb6f7084 100644
--- a/fdbclient/DatabaseConfiguration.h
+++ b/fdbclient/DatabaseConfiguration.h
@@ -333,6 +333,8 @@ private:
 
 	/// Check if the key is overridden by either mutableConfiguration or rawConfiguration
 	bool isOverridden(std::string key) const;
+	// Overwrite commitProxyCount and/or grvProxyCount if set to -1
+	void overwriteProxiesCount();
 };
 
 #endif
diff --git a/flow/Arena.h b/flow/Arena.h
index 4b5bfa9c52..a29f07f1e4 100644
--- a/flow/Arena.h
+++ b/flow/Arena.h
@@ -447,6 +447,7 @@ public:
 	const uint8_t* begin() const { return data; }
 	const uint8_t* end() const { return data + length; }
 	int size() const { return length; }
+	bool empty() const { return length == 0; }
 
 	uint8_t operator[](int i) const { return data[i]; }