diff --git a/.circleci/template.yml b/.circleci/template.yml
index 39537a18724..510396408a6 100644
--- a/.circleci/template.yml
+++ b/.circleci/template.yml
@@ -591,7 +591,7 @@ jobs:
       preset:
         type: enum
         enum: [internal_mnesia, mysql_redis, odbc_mssql_mnesia, ldap_mnesia,
-               elasticsearch_and_cassandra_mnesia, pgsql_mnesia, internal_cets]
+               elasticsearch_and_cassandra_mnesia, pgsql_mnesia, pgsql_cets]
         description: Preset to run
         default: internal_mnesia
       db:
@@ -826,11 +826,11 @@ workflows:
             - otp_25_docker
           filters: *all_tags
       - big_tests_in_docker:
-          name: internal_cets_25
-          executor: otp_25_redis
+          name: pgsql_cets_25
+          executor: otp_25_pgsql_redis
           context: mongooseim-org
-          preset: internal_cets
-          db: "mnesia cets"
+          preset: pgsql_cets
+          db: "mnesia postgres cets"
           requires:
             - otp_25_docker
           filters: *all_tags
diff --git a/big_tests/default.spec b/big_tests/default.spec
index 09686a6f466..7cd97facc0e 100644
--- a/big_tests/default.spec
+++ b/big_tests/default.spec
@@ -116,6 +116,7 @@
 {suites, "tests", dynamic_domains_SUITE}.
 {suites, "tests", local_iq_SUITE}.
 {suites, "tests", tcp_listener_SUITE}.
+{suites, "tests", cets_disco_SUITE}.
 
 {config, ["test.config"]}.
 {logdir, "ct_report"}.
diff --git a/big_tests/dynamic_domains.spec b/big_tests/dynamic_domains.spec
index 3710a19c6e5..8ec9e987850 100644
--- a/big_tests/dynamic_domains.spec
+++ b/big_tests/dynamic_domains.spec
@@ -158,6 +158,7 @@
 {suites, "tests", domain_removal_SUITE}.
 {suites, "tests", local_iq_SUITE}.
 {suites, "tests", tcp_listener_SUITE}.
+{suites, "tests", cets_disco_SUITE}.
 
 {config, ["dynamic_domains.config", "test.config"]}.
 
diff --git a/big_tests/test.config b/big_tests/test.config
index 377df5020e4..3ea5695ba62 100644
--- a/big_tests/test.config
+++ b/big_tests/test.config
@@ -237,13 +237,31 @@
       {outgoing_pools, "[outgoing_pools.redis.global_distrib]
   scope = \"global\"
   workers = 10"}]},
-    {internal_cets,
-     [{dbs, [redis]},
+    {pgsql_cets,
+     [{dbs, [redis, pgsql]},
       {sm_backend, "\"cets\""},
       {stream_management_backend, cets},
+      {auth_method, "rdbms"},
+      {internal_databases, "[internal_databases.cets]
+  cluster_name = \"{{cluster_name}}\""},
       {outgoing_pools, "[outgoing_pools.redis.global_distrib]
   scope = \"global\"
-  workers = 10"}]},
+  workers = 10
+[outgoing_pools.rdbms.default]
+  scope = \"global\"
+  workers = 5
+  connection.driver = \"pgsql\"
+  connection.host = \"localhost\"
+  connection.database = \"ejabberd\"
+  connection.username = \"ejabberd\"
+  connection.password = \"mongooseim_secret\"
+  connection.tls.required = true
+  connection.tls.cacertfile = \"priv/ssl/cacert.pem\"
+  connection.tls.server_name_indication.enabled = false"},
+      {service_domain_db, ""},
+      {mod_vcard, "  backend = \"rdbms\"
+  host = \"vjud.@HOST@\"\n"},
+      {mod_roster, "  backend = \"rdbms\"\n"}]},
     {pgsql_mnesia,
      [{dbs, [redis, pgsql]},
       {auth_method, "rdbms"},
diff --git a/big_tests/tests/cets_disco_SUITE.erl b/big_tests/tests/cets_disco_SUITE.erl
new file mode 100644
index 00000000000..b8efd04986e
--- /dev/null
+++ b/big_tests/tests/cets_disco_SUITE.erl
@@ -0,0 +1,72 @@
+-module(cets_disco_SUITE).
+-compile([export_all, nowarn_export_all]).
+
+-import(distributed_helper, [mim/0, rpc/4]).
+-include_lib("common_test/include/ct.hrl").
+
+%%--------------------------------------------------------------------
+%% Suite configuration
+%%--------------------------------------------------------------------
+
+all() ->
+    [{group, file}, {group, rdbms}].
+
+groups() ->
+    [{file, [], file_cases()},
+     {rdbms, [], rdbms_cases()}].
+
+file_cases() ->
+    [file_backend].
+
+rdbms_cases() ->
+    [rdbms_backend].
+
+suite() ->
+    escalus:suite().
+
+%%--------------------------------------------------------------------
+%% Init & teardown
+%%--------------------------------------------------------------------
+init_per_suite(Config) ->
+    escalus:init_per_suite(Config).
+
+end_per_suite(Config) ->
+    escalus:end_per_suite(Config).
+
+init_per_group(rdbms, Config) ->
+    case not ct_helper:is_ct_running()
+         orelse mongoose_helper:is_rdbms_enabled(domain_helper:host_type()) of
+        false -> {skip, rdbms_or_ct_not_running};
+        true -> Config
+    end;
+init_per_group(_, Config) ->
+    Config.
+
+end_per_group(_, Config) ->
+    Config.
+
+init_per_testcase(CaseName, Config) ->
+    escalus:init_per_testcase(CaseName, Config).
+
+end_per_testcase(CaseName, Config) ->
+    escalus:end_per_testcase(CaseName, Config).
+
+%%--------------------------------------------------------------------
+%% Test cases
+%%--------------------------------------------------------------------
+
+file_backend(Config) ->
+    Path = filename:join(?config(mim_data_dir, Config), "nodes.txt"),
+    Opts = #{disco_file => Path},
+    State = rpc(mim(), cets_discovery_file, init, [Opts]),
+    {{ok, Nodes}, _} = rpc(mim(), cets_discovery_file, get_nodes, [State]),
+    ['node1@localhost', 'node2@otherhost'] = lists:sort(Nodes).
+
+rdbms_backend(_Config) ->
+    Opts1 = #{cluster_name => <<"big_test">>, node_name_to_insert => <<"test1">>},
+    Opts2 = #{cluster_name => <<"big_test">>, node_name_to_insert => <<"test2">>},
+    State1 = rpc(mim(), mongoose_cets_discovery_rdbms, init, [Opts1]),
+    rpc(mim(), mongoose_cets_discovery_rdbms, get_nodes, [State1]),
+    State2 = rpc(mim(), mongoose_cets_discovery_rdbms, init, [Opts2]),
+    {{ok, Nodes}, _} = rpc(mim(), mongoose_cets_discovery_rdbms, get_nodes, [State2]),
+    [test1, test2] = lists:sort(Nodes).
diff --git a/big_tests/tests/cets_disco_SUITE_data/nodes.txt b/big_tests/tests/cets_disco_SUITE_data/nodes.txt
new file mode 100644
index 00000000000..8e85e526bd8
--- /dev/null
+++ b/big_tests/tests/cets_disco_SUITE_data/nodes.txt
@@ -0,0 +1,2 @@
+node1@localhost
+node2@otherhost
diff --git a/doc/configuration/configuration-files.md b/doc/configuration/configuration-files.md
index 35712ed2021..75b4e6ed366 100644
--- a/doc/configuration/configuration-files.md
+++ b/doc/configuration/configuration-files.md
@@ -15,6 +15,7 @@ The file is divided into the following sections:
 * [**general**](general.md) - Served XMPP domains, log level, server language and some other miscellaneous settings.
 * [**listen**](listen.md) - Configured listeners, receiving incoming XMPP and HTTP connections.
 * [**auth**](auth.md) - Supported client authentication methods and their options.
+* [**internal_databases**](internal-databases.md) - Options for Mnesia and CETS. They are primarily used for clustering.
 * [**outgoing_pools**](outgoing-connections.md) - Outgoing connections to external services, including databases, message queues and HTTP services.
 * [**services**](Services.md) - Internal services like an administration API and system metrics.
 * [**modules**](Modules.md) - [XMPP extension](https://xmpp.org/extensions/) modules, which extend the basic functionality provided by XMPP.
diff --git a/doc/configuration/internal-databases.md b/doc/configuration/internal-databases.md
new file mode 100644
index 00000000000..91435a9e627
--- /dev/null
+++ b/doc/configuration/internal-databases.md
@@ -0,0 +1,67 @@
+Internal databases are used to cluster MongooseIM nodes, and to replicate session list data between them.
+
+Mnesia is a legacy way to cluster MongooseIM nodes. It is also could be used to store persistent data, but we recommend
+to use RDBMS databases instead because of scalability and stability reasons.
+
+CETS is a new way to cluster MongooseIM nodes.
+CETS needs to know a list of nodes for the node discovery. There are two ways to get a list of nodes:
+
+- A text file with a list of nodes on each line. It is useful when there is an external script to make this file based on
+  some custom logic (for example, a bash script that uses AWS CLI to discover instances in the autoscaling group). This file
+  would be automatilly reread on change.
+- RDBMS database. MongooseIM would write into RDBMS its nodename and read a list of other nodes. It is pretty simple, but
+  RDBMS database could be a single point of failure.
+
+Section example:
+
+```toml
+[internal_databases]
+    [internal_databases.mnesia]
+
+    [internal_databases.cets]
+        backend = "rdbms"
+        cluster_name = "mongooseim"
+```
+
+or
+
+```toml
+[internal_databases]
+    [internal_databases.cets]
+        backend = "file"
+        node_list_file = "cets_disco.txt"
+```
+
+To enable just CETS, define only `internal_databases.cets` section:
+
+```toml
+[internal_databases]
+    [internal_databases.cets]
+```
+
+# CETS Options
+
+### `internal_databases.cets.backend`
+
+Backend for CETS discovery.
+
+* **Syntax:** string, one of `"rdbms"`, `"file"`.
+* **Default:** `"rdbms"`
+* **Example:** `backend = "rdbms"`
+
+### `internal_databases.cets.cluster_name`
+
+Namespace for the cluster. Only nodes with the same cluster name would be discoverd. This option is for RDBMS backend.
+
+* **Syntax:** string.
+* **Default:** `"mongooseim"`
+* **Example:** `cluster_name = "mongooseim"`
+
+### `internal_databases.cets.node_list_file`
+
+File to read a list of nodes from. Relative to the MongooseIM's release directory. This option is for the file backend.
+Required, if `backend = "file"`.
+
+* **Syntax:** path.
+* **Default:** not specified.
+* **Example:** `node_list_file = "/etc/mim_nodes.txt"`
diff --git a/mkdocs.yml b/mkdocs.yml
index b61f6a8f7a5..1f947362739 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -69,6 +69,7 @@ nav:
       - 'Options: General': 'configuration/general.md'
       - 'Options: Listen': 'configuration/listen.md'
       - 'Options: Auth': 'configuration/auth.md'
+      - 'Options: Internal Databases': 'configuration/internal-databases.md'
       - 'Options: Outgoing connections': 'configuration/outgoing-connections.md'
       - 'Options: Services': 'configuration/Services.md'
       - 'Options: Extension Modules': 'configuration/Modules.md'
diff --git a/priv/mssql2012.sql b/priv/mssql2012.sql
index 351939358f7..605aa69bb85 100644
--- a/priv/mssql2012.sql
+++ b/priv/mssql2012.sql
@@ -752,3 +752,10 @@ CREATE TABLE domain_events (
     domain VARCHAR(250) NOT NULL
 );
 CREATE INDEX i_domain_events_domain ON domain_events(domain);
+
+CREATE TABLE discovery_nodes (
+    node_name varchar(250),
+    cluster_name varchar(250),
+    updated_timestamp BIGINT NOT NULL, -- in microseconds
+    PRIMARY KEY (cluster_name, node_name)
+);
diff --git a/priv/mysql.sql b/priv/mysql.sql
index f3f7ed00023..4b619a3b8b7 100644
--- a/priv/mysql.sql
+++ b/priv/mysql.sql
@@ -544,3 +544,10 @@ CREATE TABLE domain_events (
     domain VARCHAR(250) NOT NULL
 );
 CREATE INDEX i_domain_events_domain ON domain_events(domain);
+
+CREATE TABLE discovery_nodes (
+    node_name varchar(250),
+    cluster_name varchar(250),
+    updated_timestamp BIGINT NOT NULL, -- in microseconds
+    PRIMARY KEY (cluster_name, node_name)
+);
diff --git a/priv/pg.sql b/priv/pg.sql
index d0525f57c84..7aa5924ec04 100644
--- a/priv/pg.sql
+++ b/priv/pg.sql
@@ -504,3 +504,10 @@ CREATE TABLE domain_events (
     PRIMARY KEY(id)
 );
 CREATE INDEX i_domain_events_domain ON domain_events(domain);
+
+CREATE TABLE discovery_nodes (
+    node_name varchar(250),
+    cluster_name varchar(250),
+    updated_timestamp BIGINT NOT NULL, -- in microseconds
+    PRIMARY KEY (cluster_name, node_name)
+);
diff --git a/rel/fed1.vars-toml.config b/rel/fed1.vars-toml.config
index b6e34e8d401..34c4b2420f3 100644
--- a/rel/fed1.vars-toml.config
+++ b/rel/fed1.vars-toml.config
@@ -17,6 +17,7 @@
 %% "localhost" host should NOT be defined.
 {hosts, "\"fed1\""}.
 {default_server_domain, "\"fed1\""}.
+{cluster_name, "fed"}.
 
 %% domain.example.com is for multitenancy preset, muc_SUITE:register_over_s2s
 {s2s_addr, "[[s2s.address]]
diff --git a/rel/files/mongooseim.toml b/rel/files/mongooseim.toml
index eb6bc696879..fea8ca43c63 100644
--- a/rel/files/mongooseim.toml
+++ b/rel/files/mongooseim.toml
@@ -162,6 +162,8 @@
     {{{auth_method_opts}}}{{/auth_method_opts}}
   {{/auth_method}}
 
+{{{internal_databases}}}
+
 {{#outgoing_pools}}
 {{{outgoing_pools}}}
 {{/outgoing_pools}}
diff --git a/rel/mim1.vars-toml.config b/rel/mim1.vars-toml.config
index 5fcea75ba4c..0cf2e6bbd8c 100644
--- a/rel/mim1.vars-toml.config
+++ b/rel/mim1.vars-toml.config
@@ -20,6 +20,7 @@
 {hosts, "\"localhost\", \"anonymous.localhost\", \"localhost.bis\""}.
 {host_types, "\"test type\", \"dummy auth\", \"anonymous\""}.
 {default_server_domain, "\"localhost\""}.
+{cluster_name, "mim"}.
 
 {mod_amp, ""}.
 {host_config,
diff --git a/rel/mim2.vars-toml.config b/rel/mim2.vars-toml.config
index 2581a209a45..758de03b341 100644
--- a/rel/mim2.vars-toml.config
+++ b/rel/mim2.vars-toml.config
@@ -18,6 +18,7 @@
 {hosts, "\"localhost\", \"anonymous.localhost\", \"localhost.bis\""}.
 {host_types, "\"test type\", \"dummy auth\""}.
 {default_server_domain, "\"localhost\""}.
+{cluster_name, "mim"}.
 {s2s_addr, "[[s2s.address]]
     host = \"localhost2\"
     ip_address = \"127.0.0.1\""}.
diff --git a/rel/mim3.vars-toml.config b/rel/mim3.vars-toml.config
index 645ea41e1cc..6e758440aa6 100644
--- a/rel/mim3.vars-toml.config
+++ b/rel/mim3.vars-toml.config
@@ -20,6 +20,7 @@
 
 {hosts, "\"localhost\", \"anonymous.localhost\", \"localhost.bis\""}.
 {default_server_domain, "\"localhost\""}.
+{cluster_name, "mim"}.
 
 {s2s_addr, "[[s2s.address]]
     host = \"localhost2\"
diff --git a/rel/reg1.vars-toml.config b/rel/reg1.vars-toml.config
index 4b5a4e4fea7..da485e138c5 100644
--- a/rel/reg1.vars-toml.config
+++ b/rel/reg1.vars-toml.config
@@ -21,6 +21,8 @@
 %% "reg1" is a local host.
 {hosts, "\"reg1\", \"localhost\""}.
 {default_server_domain, "\"reg1\""}.
+{cluster_name, "reg"}.
+
 {s2s_addr, "[[s2s.address]]
     host = \"localhost\"
     ip_address = \"127.0.0.1\"
diff --git a/rel/vars-toml.config b/rel/vars-toml.config
index d17f75d1fcb..4d5e1b235b1 100644
--- a/rel/vars-toml.config
+++ b/rel/vars-toml.config
@@ -17,6 +17,8 @@
 {http_api_client_endpoint, "port = {{ http_api_client_endpoint_port }}"}.
 {s2s_use_starttls, "\"optional\""}.
 {s2s_certfile, "\"priv/ssl/fake_server.pem\""}.
+{internal_databases, "[internal_databases]
+    [internal_databases.mnesia]"}.
 
 "./configure.vars.config".
 
diff --git a/src/config/mongoose_config_spec.erl b/src/config/mongoose_config_spec.erl
index 1ed67738942..34e5e615291 100644
--- a/src/config/mongoose_config_spec.erl
+++ b/src/config/mongoose_config_spec.erl
@@ -91,6 +91,7 @@ root() ->
                  <<"listen">> => Listen#section{include = always},
                  <<"auth">> => Auth#section{include = always},
                  <<"outgoing_pools">> => outgoing_pools(),
+                 <<"internal_databases">> => internal_databases(),
                  <<"services">> => services(),
                  <<"modules">> => Modules#section{include = always},
                  <<"shaper">> => shaper(),
@@ -425,6 +426,32 @@ auth_password() ->
        include = always
       }.
 
+%% path: internal_databases
+internal_databases() ->
+    Items = #{<<"cets">> => internal_database_cets(),
+              <<"mnesia">> => internal_database_mnesia()},
+    #section{items = Items,
+             format_items = map,
+             wrap = global_config,
+             include = always}.
+
+%% path: internal_databases.*.*
+internal_database_cets() ->
+    #section{
+       items = #{<<"backend">> => #option{type = atom,
+                                          validate = {enum, [file, rdbms]}},
+                 <<"cluster_name">> => #option{type = atom, validate = non_empty},
+                 %% Relative to the release directory (or an absolute name)
+                 <<"node_list_file">> => #option{type = string,
+                                                 validate = filename}
+                },
+       defaults = #{<<"backend">> => rdbms, <<"cluster_name">> => mongooseim}
+      }.
+
+%% path: internal_databases.*.*
+internal_database_mnesia() ->
+    #section{}.
+
 %% path: outgoing_pools
 outgoing_pools() ->
     PoolTypes = [<<"cassandra">>, <<"elastic">>, <<"http">>, <<"ldap">>,
diff --git a/src/ejabberd_sup.erl b/src/ejabberd_sup.erl
index 5b1cb95812d..f81fc5ea940 100644
--- a/src/ejabberd_sup.erl
+++ b/src/ejabberd_sup.erl
@@ -153,16 +153,9 @@ init([]) ->
         {pg,
           {pg, start_link, [mim_scope]},
           permanent, infinity, supervisor, [pg]},
-    ConfigDir = filename:dirname(mongoose_config:get_config_path()),
-    DiscoFile = filename:join(ConfigDir, "cets_disco.txt"),
-    DiscoOpts = #{name => mongoose_cets_discovery, disco_file => DiscoFile},
-    CetsDisco =
-        {cets_discovery,
-          {cets_discovery, start_link, [DiscoOpts]},
-          permanent, infinity, supervisor, [cets_discovery]},
     {ok, {{one_for_one, 10, 1},
-          [CetsDisco,
-           PG,
+          cets_specs() ++
+          [PG,
            Hooks,
            Cleaner,
            SMBackendSupervisor,
@@ -195,3 +188,34 @@ stop_child(Proc) ->
     supervisor:terminate_child(ejabberd_sup, Proc),
     supervisor:delete_child(ejabberd_sup, Proc),
     ok.
+
+cets_specs() ->
+    cets_specs(mongoose_config:get_opt([internal_databases, cets], disabled)).
+
+cets_specs(disabled) ->
+    [];
+cets_specs(#{backend := DiscoBackend, cluster_name := ClusterName} = Opts) ->
+    DiscoFile =
+        case {DiscoBackend, Opts} of
+            {file, #{node_list_file := NodeFile}} ->
+                NodeFile;
+            {file, _} ->
+                ?LOG_CRITICAL(#{what => node_list_file_option_is_required,
+                                text => <<"Specify internal_databases.cets.node_list_file option">>}),
+                error(node_list_file_option_is_required);
+            _ ->
+                undefined
+        end,
+    DiscoOpts = #{
+        backend_module => disco_backend_to_module(DiscoBackend),
+        cluster_name => atom_to_binary(ClusterName),
+        node_name_to_insert => atom_to_binary(node(), latin1),
+        name => mongoose_cets_discovery, disco_file => DiscoFile},
+    CetsDisco =
+        {cets_discovery,
+          {cets_discovery, start_link, [DiscoOpts]},
+          permanent, infinity, supervisor, [cets_discovery]},
+    [CetsDisco].
+
+disco_backend_to_module(rdbms) -> mongoose_cets_discovery_rdbms;
+disco_backend_to_module(file) -> cets_discovery_file.
diff --git a/src/mongoose_cets_discovery_rdbms.erl b/src/mongoose_cets_discovery_rdbms.erl
new file mode 100644
index 00000000000..106c4e2d91b
--- /dev/null
+++ b/src/mongoose_cets_discovery_rdbms.erl
@@ -0,0 +1,56 @@
+%% @doc MongooseIM RDBMS backend for cets_discovery.
+-module(mongoose_cets_discovery_rdbms).
+-behaviour(cets_discovery).
+-export([init/1, get_nodes/1]).
+
+-include_lib("kernel/include/logger.hrl").
+
+-type opts() :: #{cluster_name => binary(), node_name_to_insert => binary()}.
+-type state() :: opts().
+
+-spec init(opts()) -> state().
+init(Opts = #{cluster_name := _, node_name_to_insert := _}) ->
+    Opts.
+
+-spec get_nodes(state()) -> {cets_discovery:get_nodes_result(), state()}.
+get_nodes(State = #{cluster_name := ClusterName, node_name_to_insert := Node}) ->
+    prepare(),
+    insert(ClusterName, Node),
+    try mongoose_rdbms:execute_successfully(global, cets_disco_select, [ClusterName]) of
+        {selected, Rows} ->
+            Nodes = [binary_to_atom(X) || {X} <- Rows, X =/= <<>>],
+            {{ok, Nodes}, State}
+        catch Class:Reason:Stacktrace ->
+                ?LOG_ERROR(#{
+                    what => discovery_failed_select,
+                    class => Class,
+                    reason => Reason,
+                    stacktrace => Stacktrace
+                }),
+                {{error, Reason}, State}
+    end.
+
+prepare() ->
+    Filter = [<<"node_name">>, <<"cluster_name">>],
+    Fields = [<<"updated_timestamp">>],
+    rdbms_queries:prepare_upsert(global, cets_disco_insert, discovery_nodes,
+                                 Filter ++ Fields, Fields, Filter),
+    mongoose_rdbms:prepare(cets_disco_select, discovery_nodes, [cluster_name],
+            <<"SELECT node_name FROM discovery_nodes WHERE cluster_name = ?">>).
+
+insert(ClusterName, Node) ->
+    Timestamp = os:system_time(microsecond),
+    Filter = [Node, ClusterName],
+    Fields = [Timestamp],
+    try 
+        {updated, _} = rdbms_queries:execute_upsert(global, cets_disco_insert,
+                                                    Filter ++ Fields, Fields,
+                                                    Filter)
+        catch Class:Reason:Stacktrace ->
+                ?LOG_ERROR(#{
+                    what => discovery_failed_insert,
+                    class => Class,
+                    reason => Reason,
+                    stacktrace => Stacktrace
+                })
+    end.
diff --git a/test/common/config_parser_helper.erl b/test/common/config_parser_helper.erl
index b0de4bd1d76..f535dfdaf23 100644
--- a/test/common/config_parser_helper.erl
+++ b/test/common/config_parser_helper.erl
@@ -14,6 +14,7 @@ options("host_types") ->
       [<<"this is host type">>, <<"some host type">>,
        <<"another host type">>, <<"yet another host type">>]},
      {hosts, [<<"localhost">>]},
+     {internal_databases, #{}},
      {language, <<"en">>},
      {listen, []},
      {loglevel, warning},
@@ -62,6 +63,10 @@ options("miscellaneous") ->
      {hide_service_name, true},
      {host_types, []},
      {hosts, [<<"localhost">>, <<"anonymous.localhost">>]},
+     {internal_databases,
+          #{cets =>
+                #{backend => rdbms, cluster_name => mongooseim},
+            mnesia => #{}}},
      {language, <<"en">>},
      {listen,
       [config([listen, http],
@@ -106,6 +111,7 @@ options("modules") ->
      {hide_service_name, false},
      {host_types, []},
      {hosts, [<<"localhost">>, <<"dummy_host">>]},
+     {internal_databases, #{mnesia => #{}}},
      {language, <<"en">>},
      {listen, []},
      {loglevel, warning},
@@ -131,6 +137,10 @@ options("mongooseim-pgsql") ->
      {host_types, []},
      {hosts,
       [<<"localhost">>, <<"anonymous.localhost">>, <<"localhost.bis">>]},
+     {internal_databases,
+          #{cets =>
+                #{backend => rdbms, cluster_name => mongooseim},
+            mnesia => #{}}},
      {language, <<"en">>},
      {listen,
       [config([listen, c2s],
@@ -299,6 +309,7 @@ options("outgoing_pools") ->
      {host_types, []},
      {hosts,
       [<<"localhost">>, <<"anonymous.localhost">>, <<"localhost.bis">>]},
+     {internal_databases, #{}},
      {language, <<"en">>},
      {listen, []},
      {loglevel, warning},
@@ -370,6 +381,7 @@ options("s2s_only") ->
      {hide_service_name, false},
      {host_types, []},
      {hosts, [<<"localhost">>, <<"dummy_host">>]},
+     {internal_databases, #{}},
      {language, <<"en">>},
      {listen, []},
      {loglevel, warning},
diff --git a/test/config_parser_SUITE.erl b/test/config_parser_SUITE.erl
index be5ce8ed65b..aa8f0995b5b 100644
--- a/test/config_parser_SUITE.erl
+++ b/test/config_parser_SUITE.erl
@@ -52,6 +52,7 @@ all() ->
      {group, listen},
      {group, auth},
      {group, pool},
+     {group, internal_databases},
      {group, shaper_acl_access},
      {group, s2s},
      {group, modules},
@@ -147,6 +148,7 @@ groups() ->
                          pool_rabbit_connection,
                          pool_ldap,
                          pool_ldap_connection]},
+     {internal_databases, [parallel], [internal_database_cets]},
      {shaper_acl_access, [parallel], [shaper,
                                       acl,
                                       acl_merge_host_and_global,
@@ -1200,6 +1202,30 @@ test_fast_tls_server(P, T) ->
     ?err(T(#{<<"versions">> => [<<"tlsv1.2">>]})), % option only for just_tls
     ?err(T(#{<<"protocol_options">> => [<<>>]})).
 
+%% tests: internal_databases
+
+internal_database_cets(_Config) ->
+    CetsEnabled = #{<<"internal_databases">> => #{<<"cets">> => #{}}},
+    CetsFile = #{<<"internal_databases">> => #{<<"cets">> =>
+        #{<<"backend">> => <<"file">>, <<"node_list_file">> => <<"/dev/null">>}}},
+    %% No internal_databases section means an empty list of databases
+    ?cfg([internal_databases], #{}, #{}), % default
+    %% Empty internal_databases could be configured explicitly
+    ?cfg([internal_databases], #{}, #{<<"internal_databases">> => #{}}),
+
+    ?cfg([internal_databases, cets, backend], file,
+         #{<<"internal_databases">> => #{<<"cets">> => #{<<"backend">> => <<"file">>}}}),
+    ?cfg([internal_databases, cets, backend], rdbms,
+         #{<<"internal_databases">> => #{<<"cets">> => #{<<"cluster_name">> => <<"test">>}}}),
+
+    ?cfg([internal_databases, cets, cluster_name], mongooseim, CetsEnabled),
+    ?cfg([internal_databases, cets, node_list_file], "/dev/null", CetsFile),
+    %% If only mnesia section is defined, CETS section is not included
+    ?cfg([internal_databases], #{mnesia => #{}},
+         #{<<"internal_databases">> => #{<<"mnesia">> => #{}}}),
+    ?err(#{<<"internal_databases">> => #{<<"cets">> => #{<<"backend">> => <<"mnesia">>}}}),
+    ?err(#{<<"internal_databases">> => #{<<"cets">> => #{<<"cluster_name">> => 123}}}).
+
 %% tests: shaper, acl, access
 shaper(_Config) ->
     ?cfg([shaper, normal], #{max_rate => 1000},
diff --git a/test/config_parser_SUITE_data/miscellaneous.toml b/test/config_parser_SUITE_data/miscellaneous.toml
index b94d35fa089..15ea205eac6 100644
--- a/test/config_parser_SUITE_data/miscellaneous.toml
+++ b/test/config_parser_SUITE_data/miscellaneous.toml
@@ -80,3 +80,7 @@
   periodic_report = 300_000
   tracking_id.id = "G-12345678"
   tracking_id.secret = "Secret"
+
+[internal_databases]
+  [internal_databases.mnesia]
+  [internal_databases.cets]
diff --git a/test/config_parser_SUITE_data/modules.toml b/test/config_parser_SUITE_data/modules.toml
index f11a1a4d6a5..35713d01edd 100644
--- a/test/config_parser_SUITE_data/modules.toml
+++ b/test/config_parser_SUITE_data/modules.toml
@@ -5,6 +5,9 @@
   ]
   default_server_domain = "localhost"
 
+[internal_databases]
+  [internal_databases.mnesia]
+
 [modules.mod_adhoc]
   iqdisc.type = "one_queue"
   report_commands_node = true
diff --git a/test/config_parser_SUITE_data/mongooseim-pgsql.toml b/test/config_parser_SUITE_data/mongooseim-pgsql.toml
index ff43dc17e02..327087cc16d 100644
--- a/test/config_parser_SUITE_data/mongooseim-pgsql.toml
+++ b/test/config_parser_SUITE_data/mongooseim-pgsql.toml
@@ -12,6 +12,10 @@
   sm_backend = "mnesia"
   max_fsm_queue = 1000
 
+[internal_databases]
+  [internal_databases.mnesia]
+  [internal_databases.cets]
+
 [[listen.http]]
   port = 5280
   transport.num_acceptors = 10
diff --git a/test/mongoose_config_SUITE.erl b/test/mongoose_config_SUITE.erl
index 87d48955685..d8ea28afda8 100644
--- a/test/mongoose_config_SUITE.erl
+++ b/test/mongoose_config_SUITE.erl
@@ -177,6 +177,7 @@ minimal_config_opts() ->
      {hide_service_name, false},
      {host_types, []},
      {hosts, [<<"localhost">>]},
+     {internal_databases, #{}},
      {language, <<"en">>},
      {listen, []},
      {loglevel, warning},
diff --git a/tools/gh-actions-configure-preset.sh b/tools/gh-actions-configure-preset.sh
index 9096c5f9c08..5b1f1201e25 100755
--- a/tools/gh-actions-configure-preset.sh
+++ b/tools/gh-actions-configure-preset.sh
@@ -36,6 +36,8 @@ case "$PRESET" in
     export REL_CONFIG="with-mysql with-redis with-amqp_client" ;;
   pgsql_mnesia)
     export REL_CONFIG="with-pgsql" ;;
+  cets_mnesia)
+    export REL_CONFIG="with-pgsql" ;;
   riak_mnesia)
     export REL_CONFIG="with-riak" ;;
   ldap_mnesia)