diff --git a/src/backend/distributed/shared_library_init.c b/src/backend/distributed/shared_library_init.c
index 78e278a4e..8700345fb 100644
--- a/src/backend/distributed/shared_library_init.c
+++ b/src/backend/distributed/shared_library_init.c
@@ -44,6 +44,7 @@
 #include "distributed/relation_access_tracking.h"
 #include "distributed/run_from_same_connection.h"
 #include "distributed/query_pushdown_planning.h"
+#include "distributed/time_constants.h"
 #include "distributed/query_stats.h"
 #include "distributed/remote_commands.h"
 #include "distributed/shared_library_init.h"
@@ -371,9 +372,9 @@ RegisterCitusConfigVariables(void)
 		gettext_noop("Sets the maximum duration to connect to worker nodes."),
 		NULL,
 		&NodeConnectionTimeout,
-		5000, 10, 60 * 60 * 1000,
+		5 * MS_PER_SECOND, 10 * MS, MS_PER_HOUR,
 		PGC_USERSET,
-		GUC_UNIT_MS,
+		GUC_UNIT_MS | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	/* keeping temporarily for updates from pre-6.0 versions */
@@ -407,7 +408,7 @@ RegisterCitusConfigVariables(void)
 		&BinaryMasterCopyFormat,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -419,7 +420,7 @@ RegisterCitusConfigVariables(void)
 		&BinaryWorkerCopyFormat,
 		false,
 		PGC_SIGHUP,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -429,7 +430,7 @@ RegisterCitusConfigVariables(void)
 		&ExpireCachedShards,
 		false,
 		PGC_SIGHUP,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -440,7 +441,7 @@ RegisterCitusConfigVariables(void)
 		&EnableLocalExecution,
 		true,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -498,7 +499,7 @@ RegisterCitusConfigVariables(void)
 		&SubqueryPushdown,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -519,7 +520,7 @@ RegisterCitusConfigVariables(void)
 		&LogRemoteCommands,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -566,7 +567,7 @@ RegisterCitusConfigVariables(void)
 		&ExplainAllTasks,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -576,7 +577,7 @@ RegisterCitusConfigVariables(void)
 		&AllModificationsCommutative,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomRealVariable(
@@ -589,7 +590,7 @@ RegisterCitusConfigVariables(void)
 		&DistributedDeadlockDetectionTimeoutFactor,
 		2.0, -1.0, 1000.0,
 		PGC_SIGHUP,
-		0,
+		GUC_STANDARD,
 		ErrorIfNotASuitableDeadlockFactor, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -601,9 +602,9 @@ RegisterCitusConfigVariables(void)
 					 "determines how often recovery should run, "
 					 "use -1 to disable."),
 		&Recover2PCInterval,
-		60000, -1, 7 * 24 * 3600 * 1000,
+		60 * MS_PER_SECOND, -1, 7 * MS_PER_DAY,
 		PGC_SIGHUP,
-		GUC_UNIT_MS,
+		GUC_UNIT_MS | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -613,7 +614,7 @@ RegisterCitusConfigVariables(void)
 					 "to synchronize metadata to metadata nodes "
 					 "that are out of sync."),
 		&MetadataSyncInterval,
-		60000, 1, 7 * 24 * 3600 * 1000,
+		60 * MS_PER_SECOND, 1, 7 * MS_PER_DAY,
 		PGC_SIGHUP,
 		GUC_UNIT_MS | GUC_NO_SHOW_ALL,
 		NULL, NULL, NULL);
@@ -625,7 +626,7 @@ RegisterCitusConfigVariables(void)
 					 "to synchronize metadata to metadata nodes "
 					 "that are out of sync."),
 		&MetadataSyncRetryInterval,
-		5000, 1, 7 * 24 * 3600 * 1000,
+		5 * MS_PER_SECOND, 1, 7 * MS_PER_DAY,
 		PGC_SIGHUP,
 		GUC_UNIT_MS | GUC_NO_SHOW_ALL,
 		NULL, NULL, NULL);
@@ -705,7 +706,7 @@ RegisterCitusConfigVariables(void)
 		&EnableDeadlockPrevention,
 		true,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -715,7 +716,7 @@ RegisterCitusConfigVariables(void)
 		&EnableDDLPropagation,
 		true,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -747,7 +748,7 @@ RegisterCitusConfigVariables(void)
 		PROPSETCMD_NONE,
 		propagate_set_commands_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -766,9 +767,9 @@ RegisterCitusConfigVariables(void)
 					 "created with create_distributed_table()."),
 		NULL,
 		&ShardCount,
-		32, 1, 64000,
+		32, 1, MAX_SHARD_COUNT,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -779,9 +780,9 @@ RegisterCitusConfigVariables(void)
 					 "configuration value at sharded table creation time, "
 					 "and later reuse the initially read value."),
 		&ShardReplicationFactor,
-		1, 1, 100,
+		1, 1, MAX_SHARD_REPLICATION_FACTOR,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -796,7 +797,7 @@ RegisterCitusConfigVariables(void)
 		&ShardMaxSize,
 		1048576, 256, INT_MAX, /* max allowed size not set to MAX_KILOBYTES on purpose */
 		PGC_USERSET,
-		GUC_UNIT_KB,
+		GUC_UNIT_KB | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -821,7 +822,7 @@ RegisterCitusConfigVariables(void)
 		&MaxIntermediateResult,
 		1048576, -1, MAX_KILOBYTES,
 		PGC_USERSET,
-		GUC_UNIT_KB,
+		GUC_UNIT_KB | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -839,7 +840,7 @@ RegisterCitusConfigVariables(void)
 		&MaxAdaptiveExecutorPoolSize,
 		16, 1, INT_MAX,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -853,7 +854,7 @@ RegisterCitusConfigVariables(void)
 		&MaxWorkerNodesTracked,
 		2048, 8, INT_MAX,
 		PGC_POSTMASTER,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -866,7 +867,7 @@ RegisterCitusConfigVariables(void)
 		&RemoteTaskCheckInterval,
 		10, 1, INT_MAX,
 		PGC_USERSET,
-		GUC_UNIT_MS,
+		GUC_UNIT_MS | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -878,9 +879,9 @@ RegisterCitusConfigVariables(void)
 					 "before walking over these tasks again. This configuration "
 					 "value determines the length of that sleeping period."),
 		&TaskTrackerDelay,
-		200, 1, 100000,
+		200 * MS, 1, 100 * MS_PER_SECOND,
 		PGC_SIGHUP,
-		GUC_UNIT_MS,
+		GUC_UNIT_MS | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -894,7 +895,7 @@ RegisterCitusConfigVariables(void)
 		&MaxCachedConnectionsPerWorker,
 		1, 0, INT_MAX,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -908,7 +909,7 @@ RegisterCitusConfigVariables(void)
 		&MaxAssignTaskBatchSize,
 		64, 1, INT_MAX,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -922,7 +923,7 @@ RegisterCitusConfigVariables(void)
 		&MaxTrackedTasksPerNode,
 		1024, 8, INT_MAX,
 		PGC_POSTMASTER,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -935,7 +936,7 @@ RegisterCitusConfigVariables(void)
 		&MaxRunningTasksPerNode,
 		8, 1, INT_MAX,
 		PGC_SIGHUP,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -949,7 +950,7 @@ RegisterCitusConfigVariables(void)
 		&PartitionBufferSize,
 		8192, 0, (INT_MAX / 1024), /* result stored in int variable */
 		PGC_USERSET,
-		GUC_UNIT_KB,
+		GUC_UNIT_KB | GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomIntVariable(
@@ -974,7 +975,7 @@ RegisterCitusConfigVariables(void)
 		&LimitClauseRowFetchCount,
 		-1, -1, INT_MAX,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomRealVariable(
@@ -987,7 +988,7 @@ RegisterCitusConfigVariables(void)
 		&CountDistinctErrorRate,
 		0.0, 0.0, 1.0,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1001,7 +1002,7 @@ RegisterCitusConfigVariables(void)
 		COMMIT_PROTOCOL_2PC,
 		shard_commit_protocol_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1033,7 +1034,7 @@ RegisterCitusConfigVariables(void)
 		TASK_ASSIGNMENT_GREEDY,
 		task_assignment_policy_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1064,7 +1065,7 @@ RegisterCitusConfigVariables(void)
 		MULTI_EXECUTOR_ADAPTIVE,
 		task_executor_type_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -1074,7 +1075,7 @@ RegisterCitusConfigVariables(void)
 		&EnableRepartitionJoins,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1090,7 +1091,7 @@ RegisterCitusConfigVariables(void)
 		&ShardPlacementPolicy,
 		SHARD_PLACEMENT_ROUND_ROBIN, shard_placement_policy_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1100,7 +1101,7 @@ RegisterCitusConfigVariables(void)
 		&ReadFromSecondaries,
 		USE_SECONDARY_NODES_NEVER, use_secondary_nodes_options,
 		PGC_SU_BACKEND,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1110,7 +1111,7 @@ RegisterCitusConfigVariables(void)
 		&MultiTaskQueryLogLevel,
 		MULTI_TASK_QUERY_INFO_OFF, multi_task_query_log_level_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomEnumVariable(
@@ -1120,7 +1121,7 @@ RegisterCitusConfigVariables(void)
 		&MultiShardConnectionType,
 		PARALLEL_CONNECTION, multi_shard_modify_connection_options,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomStringVariable(
@@ -1130,7 +1131,7 @@ RegisterCitusConfigVariables(void)
 		&CitusVersion,
 		CITUS_VERSION,
 		PGC_INTERNAL,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomStringVariable(
@@ -1140,7 +1141,7 @@ RegisterCitusConfigVariables(void)
 		&CurrentCluster,
 		"default",
 		PGC_SU_BACKEND,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -1150,7 +1151,7 @@ RegisterCitusConfigVariables(void)
 		&WritableStandbyCoordinator,
 		false,
 		PGC_USERSET,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
@@ -1215,7 +1216,7 @@ RegisterCitusConfigVariables(void)
 		&MaxTaskStringSize,
 		12288, 8192, 65536,
 		PGC_POSTMASTER,
-		0,
+		GUC_STANDARD,
 		NULL, NULL, NULL);
 
 	DefineCustomBoolVariable(
diff --git a/src/include/distributed/shared_library_init.h b/src/include/distributed/shared_library_init.h
index a50e8db99..b5bc09da3 100644
--- a/src/include/distributed/shared_library_init.h
+++ b/src/include/distributed/shared_library_init.h
@@ -11,6 +11,10 @@
 #ifndef SHARED_LIBRARY_INIT_H
 #define SHARED_LIBRARY_INIT_H
 
+#define GUC_STANDARD 0
+#define MAX_SHARD_COUNT 64000
+#define MAX_SHARD_REPLICATION_FACTOR 100
+
 extern void StartupCitusBackend(void);
 
 #endif /* SHARED_LIBRARY_INIT_H */
diff --git a/src/include/distributed/time_constants.h b/src/include/distributed/time_constants.h
new file mode 100644
index 000000000..0406cd4a9
--- /dev/null
+++ b/src/include/distributed/time_constants.h
@@ -0,0 +1,18 @@
+/*-------------------------------------------------------------------------
+ * time_constants.h
+ *
+ * Copyright (c) Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef TIME_CONSTANTS_H
+#define TIME_CONSTANTS_H
+
+#define MS 1
+#define MS_PER_SECOND MS * 1000
+#define MS_PER_MINUTE MS_PER_SECOND * 60
+#define MS_PER_HOUR MS_PER_MINUTE * 60
+#define MS_PER_DAY MS_PER_HOUR * 24
+
+#endif /* TIME_CONSTANTS_H */