{
  config,
  pkgs,
  lib,
  ...
}:

let
  cfg = config.services.matrix-synapse;
  workers = lib.range 0 (cfg.syncWorkers - 1);
  routes = [
    "~ ^/_matrix/client/(v2_alpha|r0|v3)/sync$"
    "~ ^/_matrix/client/(api/v1|v2_alpha|r0|v3)/events$"
    "~ ^/_matrix/client/(api/v1|r0|v3)/initialSync$"
    "~ ^/_matrix/client/(api/v1|r0|v3)/rooms/[^/]+/initialSync$"
  ];
in
{
  config = lib.mkIf (cfg.syncWorkers > 0) {
    services.matrix-synapse = {
      settings = {
        instance_map = lib.listToAttrs (
          lib.map (index: {
            name = "sync-${toString index}";
            value = {
              path = "/run/matrix-synapse/sync-${toString index}.sock";
            };
          }) workers
        );
      };

      workers = lib.listToAttrs (
        lib.map (index: {
          name = "sync-${toString index}";
          value = {
            worker_app = "synapse.app.generic_worker";
            worker_listeners = [
              {
                type = "http";
                path = "/run/matrix-synapse/sync-${toString index}.sock";
                resources = [
                  {
                    names = [ "replication" ];
                    compress = false;
                  }
                ];
              }
              {
                type = "http";
                path = "/run/matrix-synapse/sync-client-${toString index}.sock";
                mode = "666";
                resources = [
                  {
                    names = [ "client" ];
                    compress = false;
                  }
                ];
              }
            ];
            database = (
              import ../db.nix {
                workerName = "sync-${toString index}";
                dbGroup = "small";
              }
            );
          };
        }) workers
      );
    };

    services.nginx.upstreams."sync" = {
      extraConfig = ''
        keepalive 32;
      '';
      servers = lib.listToAttrs (
        lib.map (index: {
          name = "unix:/run/matrix-synapse/sync-client-${toString index}.sock";
          value = {
            max_fails = 0;
          };
        }) workers
      );
    };

    services.nginx.virtualHosts."${cfg.nginxVirtualHostName}".locations = lib.listToAttrs (
      lib.map (route: {
        name = route;
        value = {
          proxyPass = "http://sync";
        };
      }) routes
    );
  };
}