diff --git a/schema/mysql/schema.sql b/schema/mysql/schema.sql
index 27f1ef5c..3f4f2889 100644
--- a/schema/mysql/schema.sql
+++ b/schema/mysql/schema.sql
@@ -10,6 +10,7 @@ CREATE TABLE available_channel_type (
 
 CREATE TABLE channel (
     id bigint NOT NULL AUTO_INCREMENT,
+    external_uuid char(36) NOT NULL, -- used for external references, lower case
     name text NOT NULL COLLATE utf8mb4_unicode_ci,
     type varchar(255) NOT NULL, -- 'email', 'sms', ...
     config mediumtext, -- JSON with channel-specific attributes
@@ -20,6 +21,7 @@ CREATE TABLE channel (
     deleted enum('n', 'y') NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_channel PRIMARY KEY (id),
+    CONSTRAINT uk_channel_external_uuid UNIQUE (external_uuid),
     CONSTRAINT fk_channel_available_channel_type FOREIGN KEY (type) REFERENCES available_channel_type(type)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
 
@@ -27,6 +29,7 @@ CREATE INDEX idx_channel_changed_at ON channel(changed_at);
 
 CREATE TABLE contact (
     id bigint NOT NULL AUTO_INCREMENT,
+    external_uuid char(36) NOT NULL, -- used for external references, lower case
     full_name text NOT NULL COLLATE utf8mb4_unicode_ci,
     username varchar(254) COLLATE utf8mb4_unicode_ci, -- reference to web user
     default_channel_id bigint NOT NULL,
@@ -35,6 +38,7 @@ CREATE TABLE contact (
     deleted enum('n', 'y') NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_contact PRIMARY KEY (id),
+    CONSTRAINT uk_contact_external_uuid UNIQUE (external_uuid),
 
     -- As the username is unique, it must be NULLed for deletion via "deleted = 'y'"
     CONSTRAINT uk_contact_username UNIQUE (username),
@@ -61,12 +65,14 @@ CREATE INDEX idx_contact_address_changed_at ON contact_address(changed_at);
 
 CREATE TABLE contactgroup (
     id bigint NOT NULL AUTO_INCREMENT,
+    external_uuid char(36) NOT NULL, -- used for external references, lower case
     name text NOT NULL COLLATE utf8mb4_unicode_ci,
 
     changed_at bigint NOT NULL,
     deleted enum('n', 'y') NOT NULL DEFAULT 'n',
 
-    CONSTRAINT pk_contactgroup PRIMARY KEY (id)
+    CONSTRAINT pk_contactgroup PRIMARY KEY (id),
+    CONSTRAINT uk_contactgroup_external_uuid UNIQUE (external_uuid)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
 
 CREATE INDEX idx_contactgroup_changed_at ON contactgroup(changed_at);
diff --git a/schema/mysql/upgrades/0.2.0-external-uuid.sql b/schema/mysql/upgrades/0.2.0-external-uuid.sql
new file mode 100644
index 00000000..750bdd4e
--- /dev/null
+++ b/schema/mysql/upgrades/0.2.0-external-uuid.sql
@@ -0,0 +1,15 @@
+ALTER TABLE contact ADD COLUMN external_uuid char(36) AFTER id;
+ALTER TABLE contactgroup ADD COLUMN external_uuid char(36) AFTER id;
+ALTER TABLE channel ADD COLUMN external_uuid char(36) AFTER id;
+
+UPDATE contact SET external_uuid = UUID() WHERE external_uuid IS NULL;
+UPDATE contactgroup SET external_uuid = UUID() WHERE external_uuid IS NULL;
+UPDATE channel SET external_uuid = UUID() WHERE external_uuid IS NULL;
+
+ALTER TABLE contact MODIFY COLUMN external_uuid char(36) NOT NULL;
+ALTER TABLE contactgroup MODIFY COLUMN external_uuid char(36) NOT NULL;
+ALTER TABLE channel MODIFY COLUMN external_uuid char(36) NOT NULL;
+
+ALTER TABLE contact ADD CONSTRAINT uk_contact_external_uuid UNIQUE (external_uuid);
+ALTER TABLE contactgroup ADD CONSTRAINT uk_contactgroup_external_uuid UNIQUE (external_uuid);
+ALTER TABLE channel ADD CONSTRAINT uk_channel_external_uuid UNIQUE (external_uuid);
diff --git a/schema/pgsql/schema.sql b/schema/pgsql/schema.sql
index 5ddb12e7..3f2d943c 100644
--- a/schema/pgsql/schema.sql
+++ b/schema/pgsql/schema.sql
@@ -42,6 +42,7 @@ CREATE TABLE available_channel_type (
 
 CREATE TABLE channel (
     id bigserial,
+    external_uuid uuid NOT NULL, -- used for external references
     name citext NOT NULL,
     type varchar(255) NOT NULL, -- 'email', 'sms', ...
     config text, -- JSON with channel-specific attributes
@@ -52,6 +53,7 @@ CREATE TABLE channel (
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_channel PRIMARY KEY (id),
+    CONSTRAINT uk_channel_external_uuid UNIQUE (external_uuid),
     CONSTRAINT fk_channel_available_channel_type FOREIGN KEY (type) REFERENCES available_channel_type(type)
 );
 
@@ -59,6 +61,7 @@ CREATE INDEX idx_channel_changed_at ON channel(changed_at);
 
 CREATE TABLE contact (
     id bigserial,
+    external_uuid uuid NOT NULL, -- used for external references
     full_name citext NOT NULL,
     username citext, -- reference to web user
     default_channel_id bigint NOT NULL,
@@ -67,6 +70,7 @@ CREATE TABLE contact (
     deleted boolenum NOT NULL DEFAULT 'n',
 
     CONSTRAINT pk_contact PRIMARY KEY (id),
+    CONSTRAINT uk_contact_external_uuid UNIQUE (external_uuid),
 
     -- As the username is unique, it must be NULLed for deletion via "deleted = 'y'"
     CONSTRAINT uk_contact_username UNIQUE (username),
@@ -94,12 +98,14 @@ CREATE INDEX idx_contact_address_changed_at ON contact_address(changed_at);
 
 CREATE TABLE contactgroup (
     id bigserial,
+    external_uuid uuid NOT NULL, -- used for external references
     name citext NOT NULL,
 
     changed_at bigint NOT NULL,
     deleted boolenum NOT NULL DEFAULT 'n',
 
-    CONSTRAINT pk_contactgroup PRIMARY KEY (id)
+    CONSTRAINT pk_contactgroup PRIMARY KEY (id),
+    CONSTRAINT uk_contactgroup_external_uuid UNIQUE (external_uuid)
 );
 
 CREATE INDEX idx_contactgroup_changed_at ON contactgroup(changed_at);
diff --git a/schema/pgsql/upgrades/0.2.0-external-uuid.sql b/schema/pgsql/upgrades/0.2.0-external-uuid.sql
new file mode 100644
index 00000000..a79192cf
--- /dev/null
+++ b/schema/pgsql/upgrades/0.2.0-external-uuid.sql
@@ -0,0 +1,15 @@
+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+
+ALTER TABLE contact ADD COLUMN external_uuid uuid CONSTRAINT uk_contact_external_uuid UNIQUE;
+ALTER TABLE contactgroup ADD COLUMN external_uuid uuid CONSTRAINT uk_contactgroup_external_uuid UNIQUE;
+ALTER TABLE channel ADD COLUMN external_uuid uuid CONSTRAINT uk_channel_external_uuid UNIQUE;
+
+UPDATE contact SET external_uuid = uuid_generate_v4() WHERE external_uuid IS NULL;
+UPDATE contactgroup SET external_uuid = uuid_generate_v4() WHERE external_uuid IS NULL;
+UPDATE channel SET external_uuid = uuid_generate_v4() WHERE external_uuid IS NULL;
+
+ALTER TABLE contact ALTER COLUMN external_uuid SET NOT NULL;
+ALTER TABLE contactgroup ALTER COLUMN external_uuid SET NOT NULL;
+ALTER TABLE channel ALTER COLUMN external_uuid SET NOT NULL;
+
+DROP EXTENSION "uuid-ossp";