diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 641e3ae..b6959db 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -22,15 +22,14 @@ test-frontend:
     changes:
       - frontend/*
 
-backend-sobelow:
+test-backend:
   stage: test
   image: elixir:1.9
+  variables:
+    MIX_ENV: test
   only:
     changes:
       - backend/*
-  except:
-    - develop
-    - master
   before_script:
     - cd backend
   script:
@@ -38,6 +37,7 @@ backend-sobelow:
     - mix local.rebar --force
     - mix deps.get
     - mix deps.compile
+    - mix credo --strict
     - mix sobelow --config
   cache:
     paths:
diff --git a/backend/lib/backend/api.ex b/backend/lib/backend/api.ex
index 702f17e..7ce5bea 100644
--- a/backend/lib/backend/api.ex
+++ b/backend/lib/backend/api.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Api do
+  @moduledoc """
+  Functions used in the API controllers. Most of these simply return data from the database.
+  """
   alias Backend.{Edge, Instance, Repo}
   import Backend.Util
   import Ecto.Query
@@ -67,6 +70,7 @@ defmodule Backend.Api do
   end
 
   @spec list_edges() :: [Edge.t()]
+  # credo:disable-for-next-line Credo.Check.Refactor.CyclomaticComplexity
   def list_edges(domain \\ nil) do
     user_threshold = get_config(:personal_instance_threshold)
 
diff --git a/backend/lib/backend/application.ex b/backend/lib/backend/application.ex
index f600ed4..0d84678 100644
--- a/backend/lib/backend/application.ex
+++ b/backend/lib/backend/application.ex
@@ -22,7 +22,7 @@ defmodule Backend.Application do
       # Start the endpoint when the application starts
       BackendWeb.Endpoint,
       # Crawler children
-      :hackney_pool.child_spec(:crawler, timeout: 15000, max_connections: crawl_worker_count),
+      :hackney_pool.child_spec(:crawler, timeout: 15_000, max_connections: crawl_worker_count),
       Supervisor.child_spec(
         {Task,
          fn ->
diff --git a/backend/lib/backend/auth.ex b/backend/lib/backend/auth.ex
index 211e2ae..686e6ba 100644
--- a/backend/lib/backend/auth.ex
+++ b/backend/lib/backend/auth.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Auth do
+  @moduledoc """
+  Functions related to authentication.
+  """
   alias Phoenix.Token
   import Backend.Util
 
@@ -12,6 +15,6 @@ defmodule Backend.Auth do
 
   def verify_token(token) do
     # tokens are valid for 12 hours
-    Token.verify(BackendWeb.Endpoint, @salt, token, max_age: 43200)
+    Token.verify(BackendWeb.Endpoint, @salt, token, max_age: 43_200)
   end
 end
diff --git a/backend/lib/backend/crawl.ex b/backend/lib/backend/crawl.ex
index 63ecd26..833b415 100644
--- a/backend/lib/backend/crawl.ex
+++ b/backend/lib/backend/crawl.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Crawl do
+  @moduledoc """
+  Stores aggregate data about a single crawl (i.e. not individual statuses, but the number of statuses seen etc.)
+  """
   use Ecto.Schema
   import Ecto.Changeset
 
diff --git a/backend/lib/backend/crawl_interaction.ex b/backend/lib/backend/crawl_interaction.ex
index cb29122..edb654d 100644
--- a/backend/lib/backend/crawl_interaction.ex
+++ b/backend/lib/backend/crawl_interaction.ex
@@ -1,4 +1,8 @@
 defmodule Backend.CrawlInteraction do
+  @moduledoc """
+  Model for tracking interactions between instances. Stores the source and target instance, as well as the number
+  of mentions seen in the given crawl.
+  """
   use Ecto.Schema
   import Ecto.Changeset
 
diff --git a/backend/lib/backend/crawler/crawler.ex b/backend/lib/backend/crawler/crawler.ex
index 0d3f852..d1a2e1b 100644
--- a/backend/lib/backend/crawler/crawler.ex
+++ b/backend/lib/backend/crawler/crawler.ex
@@ -4,11 +4,13 @@ defmodule Backend.Crawler do
   """
 
   alias __MODULE__
-  alias Backend.Crawler.Crawlers.{Friendica, GnuSocial, Mastodon, Misskey, Nodeinfo}
+  alias Backend.{Crawl, CrawlInteraction, Instance, InstancePeer, MostRecentCrawl, Repo}
   alias Backend.Crawler.ApiCrawler
-  alias Backend.{Crawl, CrawlInteraction, MostRecentCrawl, Repo, Instance, InstancePeer}
+  alias Backend.Crawler.Crawlers.{Friendica, GnuSocial, Mastodon, Misskey, Nodeinfo}
+
   import Ecto.Query
   import Backend.Util
+
   require Logger
 
   defstruct [
diff --git a/backend/lib/backend/crawler/crawlers/friendica.ex b/backend/lib/backend/crawler/crawlers/friendica.ex
index 5fc4abf..13884ef 100644
--- a/backend/lib/backend/crawler/crawlers/friendica.ex
+++ b/backend/lib/backend/crawler/crawlers/friendica.ex
@@ -1,4 +1,9 @@
 defmodule Backend.Crawler.Crawlers.Friendica do
+  @moduledoc """
+  A crawler for Friendica servers.
+  These don't expose a public list of statuses. This crawler combines nodeinfo data with the /statistics.json endpoint
+  in Friendica, and gets a list of peers from /poco/@server.
+  """
   alias Backend.Crawler.ApiCrawler
   import Backend.Crawler.Util
   import Backend.Util
@@ -21,7 +26,8 @@ defmodule Backend.Crawler.Crawlers.Friendica do
   @impl ApiCrawler
   def allows_crawling?(domain) do
     [
-      "/statistics.json"
+      "/statistics.json",
+      "/poco/@server"
     ]
     |> Enum.map(fn endpoint -> "https://#{domain}#{endpoint}" end)
     |> urls_are_crawlable?()
diff --git a/backend/lib/backend/crawler/crawlers/gnu_social.ex b/backend/lib/backend/crawler/crawlers/gnu_social.ex
index f292d54..1deb5c2 100644
--- a/backend/lib/backend/crawler/crawlers/gnu_social.ex
+++ b/backend/lib/backend/crawler/crawlers/gnu_social.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Crawler.Crawlers.GnuSocial do
+  @moduledoc """
+  Crawler for GNU Social servers.
+  """
   alias Backend.Crawler.ApiCrawler
   alias Backend.Crawler.Crawlers.Nodeinfo
   import Backend.Crawler.Util
diff --git a/backend/lib/backend/crawler/crawlers/mastodon.ex b/backend/lib/backend/crawler/crawlers/mastodon.ex
index a4da522..8f50c30 100644
--- a/backend/lib/backend/crawler/crawlers/mastodon.ex
+++ b/backend/lib/backend/crawler/crawlers/mastodon.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Crawler.Crawlers.Mastodon do
+  @moduledoc """
+  Crawler for the Mastodon API (used by Mastodon, its forks like Gab or Glitch, and Pleroma).
+  """
   require Logger
   import Backend.Crawler.Util
   import Backend.Util
diff --git a/backend/lib/backend/crawler/crawlers/misskey.ex b/backend/lib/backend/crawler/crawlers/misskey.ex
index a49c792..24513ca 100644
--- a/backend/lib/backend/crawler/crawlers/misskey.ex
+++ b/backend/lib/backend/crawler/crawlers/misskey.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Crawler.Crawlers.Misskey do
+  @moduledoc """
+  Crawler for Misskey servers.
+  """
   alias Backend.Crawler.ApiCrawler
 
   @behaviour ApiCrawler
diff --git a/backend/lib/backend/crawler/crawlers/nodeinfo.ex b/backend/lib/backend/crawler/crawlers/nodeinfo.ex
index bb4ab18..1f58f4f 100644
--- a/backend/lib/backend/crawler/crawlers/nodeinfo.ex
+++ b/backend/lib/backend/crawler/crawlers/nodeinfo.ex
@@ -1,9 +1,4 @@
 defmodule Backend.Crawler.Crawlers.Nodeinfo do
-  alias Backend.Crawler.ApiCrawler
-  require Logger
-  import Backend.Util
-  import Backend.Crawler.Util
-
   @moduledoc """
   This module is slightly different from the other crawlers.
   It doesn't implement the ApiCrawler spec because it isn't run as a self-contained crawler.
@@ -12,6 +7,10 @@ defmodule Backend.Crawler.Crawlers.Nodeinfo do
   This is to get the user count. Some servers don't publish this in other places (e.g. GNU Social, PeerTube) so we need
   nodeinfo to know whether it's a personal instance or not.
   """
+  alias Backend.Crawler.ApiCrawler
+  require Logger
+  import Backend.Util
+  import Backend.Crawler.Util
 
   defstruct [
     :description,
diff --git a/backend/lib/backend/crawler/stale_instance_manager.ex b/backend/lib/backend/crawler/stale_instance_manager.ex
index 8f65849..fd641e3 100644
--- a/backend/lib/backend/crawler/stale_instance_manager.ex
+++ b/backend/lib/backend/crawler/stale_instance_manager.ex
@@ -1,15 +1,15 @@
 defmodule Backend.Crawler.StaleInstanceManager do
+  @moduledoc """
+  This module regularly finds stale instances (i.e. instances that haven't been updated for longer than the crawl
+  interval) and adds them to the job queue. It runs once a minute.
+  """
+
   use GenServer
   alias Backend.{Instance, Repo}
   import Ecto.Query
   import Backend.Util
   require Logger
 
-  @moduledoc """
-  This module regularly finds stale instances (i.e. instances that haven't been updated for longer than the crawl
-  interval) and adds them to the job queue. It runs once a minute.
-  """
-
   def start_link(_opts) do
     GenServer.start_link(__MODULE__, [], name: __MODULE__)
   end
@@ -44,11 +44,11 @@ defmodule Backend.Crawler.StaleInstanceManager do
     {:noreply, state}
   end
 
-  defp schedule_add() do
+  defp schedule_add do
     Process.send_after(self(), :queue_stale_domains, 60_000)
   end
 
-  defp queue_stale_domains() do
+  defp queue_stale_domains do
     now = get_now()
 
     stale_domains =
diff --git a/backend/lib/backend/crawler/util.ex b/backend/lib/backend/crawler/util.ex
index 92297fb..f013785 100644
--- a/backend/lib/backend/crawler/util.ex
+++ b/backend/lib/backend/crawler/util.ex
@@ -1,4 +1,5 @@
 defmodule Backend.Crawler.Util do
+  @moduledoc false
   require Logger
   alias Backend.{Instance, Repo}
   import Backend.Util
diff --git a/backend/lib/backend/edge.ex b/backend/lib/backend/edge.ex
index 3182218..933b275 100644
--- a/backend/lib/backend/edge.ex
+++ b/backend/lib/backend/edge.ex
@@ -1,4 +1,5 @@
 defmodule Backend.Edge do
+  @moduledoc false
   use Ecto.Schema
   import Ecto.Changeset
 
diff --git a/backend/lib/backend/elasticsearch/cluster.ex b/backend/lib/backend/elasticsearch/cluster.ex
index fd436d9..d34a9c8 100644
--- a/backend/lib/backend/elasticsearch/cluster.ex
+++ b/backend/lib/backend/elasticsearch/cluster.ex
@@ -1,4 +1,5 @@
 defmodule Backend.Elasticsearch.Cluster do
+  @moduledoc false
   use Elasticsearch.Cluster, otp_app: :backend
 
   def init(config) do
diff --git a/backend/lib/backend/elasticsearch/store.ex b/backend/lib/backend/elasticsearch/store.ex
index a3c9b11..aa5bc98 100644
--- a/backend/lib/backend/elasticsearch/store.ex
+++ b/backend/lib/backend/elasticsearch/store.ex
@@ -1,4 +1,5 @@
 defmodule Backend.Elasticsearch.Store do
+  @moduledoc false
   @behaviour Elasticsearch.Store
 
   alias Backend.Repo
diff --git a/backend/lib/backend/instance.ex b/backend/lib/backend/instance.ex
index 5cdf7df..468e910 100644
--- a/backend/lib/backend/instance.ex
+++ b/backend/lib/backend/instance.ex
@@ -1,4 +1,8 @@
 defmodule Backend.Instance do
+  @moduledoc """
+  Model for storing everything related to an instance: not only the data from crawls, but also statistics, the time
+  of the next scheduled crawl, X and Y coordinates on the graph, and so on.
+  """
   use Ecto.Schema
   import Ecto.Changeset
 
diff --git a/backend/lib/backend/instance_peer.ex b/backend/lib/backend/instance_peer.ex
index 914bf4f..a251507 100644
--- a/backend/lib/backend/instance_peer.ex
+++ b/backend/lib/backend/instance_peer.ex
@@ -1,4 +1,8 @@
 defmodule Backend.InstancePeer do
+  @moduledoc """
+  Model for tracking which other instances a given instance knows of
+  (the data returned from /api/v1/instance/peers from Mastodon, for example)
+  """
   use Ecto.Schema
   import Ecto.Changeset
 
diff --git a/backend/lib/backend/most_recent_crawl.ex b/backend/lib/backend/most_recent_crawl.ex
index 1958ae3..63e0044 100644
--- a/backend/lib/backend/most_recent_crawl.ex
+++ b/backend/lib/backend/most_recent_crawl.ex
@@ -1,4 +1,8 @@
 defmodule Backend.MostRecentCrawl do
+  @moduledoc """
+  Model for fast access to the most recent crawl ID for a given domain.
+  You could also just look this up in the crawls table, but that table gets very large so this is much faster.
+  """
   use Ecto.Schema
   import Ecto.Changeset
 
diff --git a/backend/lib/backend/release.ex b/backend/lib/backend/release.ex
index 203926f..430ab4a 100644
--- a/backend/lib/backend/release.ex
+++ b/backend/lib/backend/release.ex
@@ -1,4 +1,8 @@
 defmodule Backend.Release do
+  @moduledoc """
+  Functions related to releases. Can be run against the compiled binary with e.g.
+  `/bin/backend eval "Backend.Release.migrate()"`
+  """
   @app :backend
   @start_apps [
     :crypto,
@@ -31,7 +35,7 @@ defmodule Backend.Release do
     {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
   end
 
-  def build_elasticsearch_indexes() do
+  def build_elasticsearch_indexes do
     start_services()
     IO.puts("Building indexes...")
     Enum.each(@indexes, &Elasticsearch.Index.hot_swap(Backend.Elasticsearch.Cluster, &1))
diff --git a/backend/lib/backend/scheduler.ex b/backend/lib/backend/scheduler.ex
index f95a693..aa711b6 100644
--- a/backend/lib/backend/scheduler.ex
+++ b/backend/lib/backend/scheduler.ex
@@ -5,9 +5,12 @@ defmodule Backend.Scheduler do
 
   use Quantum.Scheduler, otp_app: :backend
 
-  alias Backend.{Crawl, Edge, CrawlInteraction, Instance, Repo}
+  alias Backend.{Crawl, CrawlInteraction, Edge, Instance, Repo}
+  alias Backend.Mailer.AdminEmail
+
   import Backend.Util
   import Ecto.Query
+
   require Logger
 
   @doc """
@@ -34,7 +37,7 @@ defmodule Backend.Scheduler do
   Calculates every instance's "insularity score" -- that is, the percentage of mentions that are among users on the
   instance, rather than at other instances.
   """
-  def generate_insularity_scores() do
+  def generate_insularity_scores do
     now = get_now()
 
     crawls_subquery =
@@ -79,7 +82,7 @@ defmodule Backend.Scheduler do
   @doc """
   This function calculates the average number of statuses per hour over the last month.
   """
-  def generate_status_rate() do
+  def generate_status_rate do
     now = get_now()
     # We want the earliest sucessful crawl so that we can exclude it from the statistics.
     # This is because the first crawl goes up to one month into the past -- this would mess up the counts!
@@ -138,7 +141,7 @@ defmodule Backend.Scheduler do
   It calculates the strength of edges between nodes. Self-edges are not generated.
   Edges are only generated if both instances have been succesfully crawled.
   """
-  def generate_edges() do
+  def generate_edges do
     now = get_now()
 
     crawls_subquery =
@@ -177,32 +180,7 @@ defmodule Backend.Scheduler do
 
         edges =
           interactions
-          # Get a map of %{{source, target} => {total_mention_count, total_statuses_seen}}
-          |> Enum.reduce(%{}, fn
-            %{
-              source_domain: source_domain,
-              target_domain: target_domain,
-              mentions: mentions,
-              source_statuses_seen: source_statuses_seen,
-              target_statuses_seen: target_statuses_seen
-            },
-            acc ->
-              key = get_interaction_key(source_domain, target_domain)
-
-              # target_statuses_seen might be nil if that instance was never crawled. default to 0.
-              target_statuses_seen =
-                case target_statuses_seen do
-                  nil -> 0
-                  _ -> target_statuses_seen
-                end
-
-              statuses_seen = source_statuses_seen + target_statuses_seen
-
-              Map.update(acc, key, {mentions, statuses_seen}, fn {curr_mentions,
-                                                                  curr_statuses_seen} ->
-                {curr_mentions + mentions, curr_statuses_seen}
-              end)
-          end)
+          |> reduce_mention_count()
           |> Enum.map(fn {{source_domain, target_domain}, {mention_count, statuses_seen}} ->
             %{
               source_domain: source_domain,
@@ -224,7 +202,7 @@ defmodule Backend.Scheduler do
   This function checks to see if a lot of instances on the same base domain have been created recently. If so,
   notifies the server admin over SMS.
   """
-  def check_for_spam_instances() do
+  def check_for_spam_instances do
     hour_range = 3
 
     count_subquery =
@@ -264,9 +242,38 @@ defmodule Backend.Scheduler do
 
       Logger.info(message)
       send_admin_sms(message)
-      Backend.Mailer.AdminEmail.send("Potential spam", message)
+      AdminEmail.send("Potential spam", message)
     else
       Logger.debug("Did not find potential spam instances.")
     end
   end
+
+  # Takes a list of Interactions
+  # Returns a map of %{{source, target} => {total_mention_count, total_statuses_seen}}
+  defp reduce_mention_count(interactions) do
+    Enum.reduce(interactions, %{}, fn
+      %{
+        source_domain: source_domain,
+        target_domain: target_domain,
+        mentions: mentions,
+        source_statuses_seen: source_statuses_seen,
+        target_statuses_seen: target_statuses_seen
+      },
+      acc ->
+        key = get_interaction_key(source_domain, target_domain)
+
+        # target_statuses_seen might be nil if that instance was never crawled. default to 0.
+        target_statuses_seen =
+          case target_statuses_seen do
+            nil -> 0
+            _ -> target_statuses_seen
+          end
+
+        statuses_seen = source_statuses_seen + target_statuses_seen
+
+        Map.update(acc, key, {mentions, statuses_seen}, fn {curr_mentions, curr_statuses_seen} ->
+          {curr_mentions + mentions, curr_statuses_seen}
+        end)
+    end)
+  end
 end
diff --git a/backend/lib/backend/util.ex b/backend/lib/backend/util.ex
index 9d21ca0..7747450 100644
--- a/backend/lib/backend/util.ex
+++ b/backend/lib/backend/util.ex
@@ -1,4 +1,5 @@
 defmodule Backend.Util do
+  @moduledoc false
   import Ecto.Query
   require Logger
   alias Backend.{Crawl, MostRecentCrawl, Repo}
@@ -53,7 +54,7 @@ defmodule Backend.Util do
   @doc """
   Gets the current UTC time as a NaiveDateTime in a format that can be inserted into the database.
   """
-  def get_now() do
+  def get_now do
     NaiveDateTime.truncate(NaiveDateTime.utc_now(), :second)
   end
 
@@ -160,8 +161,8 @@ defmodule Backend.Util do
   def get_and_decode(url) do
     case HTTPoison.get(url, [{"User-Agent", get_config(:user_agent)}],
            hackney: [pool: :crawler],
-           recv_timeout: 15000,
-           timeout: 15000
+           recv_timeout: 15_000,
+           timeout: 15_000
          ) do
       {:ok, %{status_code: 200, body: body}} -> Jason.decode(body)
       {:ok, _} -> {:error, %HTTPoison.Error{reason: "Non-200 response"}}
@@ -185,8 +186,8 @@ defmodule Backend.Util do
   def post_and_decode(url, body \\ "") do
     case HTTPoison.post(url, body, [{"User-Agent", get_config(:user_agent)}],
            hackney: [pool: :crawler],
-           recv_timeout: 15000,
-           timeout: 15000
+           recv_timeout: 15_000,
+           timeout: 15_000
          ) do
       {:ok, %{status_code: 200, body: response_body}} -> Jason.decode(response_body)
       {:ok, _} -> {:error, %HTTPoison.Error{reason: "Non-200 response"}}
diff --git a/backend/lib/backend_web/controllers/admin_controller.ex b/backend/lib/backend_web/controllers/admin_controller.ex
index 6989b9f..784817a 100644
--- a/backend/lib/backend_web/controllers/admin_controller.ex
+++ b/backend/lib/backend_web/controllers/admin_controller.ex
@@ -1,7 +1,6 @@
 defmodule BackendWeb.AdminController do
+  alias Backend.{Api, Auth, Instance}
   use BackendWeb, :controller
-  alias Backend.{Auth, Api, Instance}
-  require Logger
 
   action_fallback BackendWeb.FallbackController
 
diff --git a/backend/lib/backend_web/controllers/admin_login_controller.ex b/backend/lib/backend_web/controllers/admin_login_controller.ex
index 7eab69a..2ef16e3 100644
--- a/backend/lib/backend_web/controllers/admin_login_controller.ex
+++ b/backend/lib/backend_web/controllers/admin_login_controller.ex
@@ -10,8 +10,6 @@ defmodule BackendWeb.AdminLoginController do
   choose one or the other by POSTing back.
   """
   def show(conn, %{"id" => domain}) do
-    # TODO: this should really be handled in a more async manner
-    # TODO: this assumes mastodon/pleroma API
     cleaned_domain = clean_domain(domain)
 
     instance_data = get_and_decode!("https://#{cleaned_domain}/api/v1/instance")
@@ -24,6 +22,7 @@ defmodule BackendWeb.AdminLoginController do
 
     instance_data = get_and_decode!("https://#{cleaned_domain}/api/v1/instance")
 
+    # credo:disable-for-lines:16 Credo.Check.Refactor.CondStatements
     error =
       cond do
         type == "email" ->
diff --git a/backend/lib/backend_web/views/instance_view.ex b/backend/lib/backend_web/views/instance_view.ex
index bb8ef8d..c7d0956 100644
--- a/backend/lib/backend_web/views/instance_view.ex
+++ b/backend/lib/backend_web/views/instance_view.ex
@@ -8,57 +8,66 @@ defmodule BackendWeb.InstanceView do
 
     cond do
       instance.user_count < user_threshold and not instance.opt_in ->
-        %{
-          name: instance.domain,
-          status: "personal instance"
-        }
+        render_personal_instance(instance)
 
       instance.crawl_error == "robots.txt" ->
-        %{
-          name: instance.domain,
-          status: instance.crawl_error
-        }
+        render_domain_and_error(instance)
 
       instance.crawl_error != nil and instance.type == nil ->
-        %{
-          name: instance.domain,
-          status: instance.crawl_error
-        }
+        render_domain_and_error(instance)
 
       true ->
-        last_updated = max_datetime(crawl.inserted_at, instance.updated_at)
-
-        filtered_peers =
-          instance.peers
-          |> Enum.filter(fn peer -> not peer.opt_out end)
-
-        statuses_per_user_per_day =
-          if instance.statuses_per_day != nil and instance.user_count != nil and
-               instance.user_count > 0 do
-            instance.statuses_per_day / instance.user_count
-          else
-            nil
-          end
-
-        %{
-          name: instance.domain,
-          description: instance.description,
-          version: instance.version,
-          userCount: instance.user_count,
-          insularity: instance.insularity,
-          statusCount: instance.status_count,
-          domainCount: length(instance.peers),
-          peers: render_many(filtered_peers, InstanceView, "instance.json"),
-          lastUpdated: last_updated,
-          status: "success",
-          type: instance.type,
-          statusesPerDay: instance.statuses_per_day,
-          statusesPerUserPerDay: statuses_per_user_per_day
-        }
+        render_instance(instance, crawl)
     end
   end
 
   def render("instance.json", %{instance: instance}) do
     %{name: instance.domain}
   end
+
+  defp render_personal_instance(instance) do
+    %{
+      name: instance.domain,
+      status: "personal instance"
+    }
+  end
+
+  defp render_domain_and_error(instance) do
+    %{
+      name: instance.domain,
+      status: instance.crawl_error
+    }
+  end
+
+  defp render_instance(instance, crawl) do
+    last_updated = max_datetime(crawl.inserted_at, instance.updated_at)
+
+    filtered_peers =
+      instance.peers
+      |> Enum.filter(fn peer -> not peer.opt_out end)
+
+    statuses_per_user_per_day =
+      if instance.statuses_per_day != nil and instance.user_count != nil and
+           instance.user_count > 0 do
+        instance.statuses_per_day / instance.user_count
+      else
+        nil
+      end
+
+    %{
+      name: instance.domain,
+      description: instance.description,
+      version: instance.version,
+      userCount: instance.user_count,
+      insularity: instance.insularity,
+      statusCount: instance.status_count,
+      domainCount: length(instance.peers),
+      peers: render_many(filtered_peers, InstanceView, "instance.json"),
+      lastUpdated: last_updated,
+      status: "success",
+      type: instance.type,
+      statusesPerDay: instance.statuses_per_day,
+      statusesPerUserPerDay: statuses_per_user_per_day
+    }
+  end
 end
diff --git a/backend/lib/mailer/admin_email.ex b/backend/lib/mailer/admin_email.ex
index 61cda11..d5ec3a9 100644
--- a/backend/lib/mailer/admin_email.ex
+++ b/backend/lib/mailer/admin_email.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Mailer.AdminEmail do
+  @moduledoc """
+  Module for sending emails to the server administrator.
+  """
   import Swoosh.Email
   import Backend.Util
   require Logger
diff --git a/backend/lib/mailer/mailer.ex b/backend/lib/mailer/mailer.ex
index c67ac2c..72c4a42 100644
--- a/backend/lib/mailer/mailer.ex
+++ b/backend/lib/mailer/mailer.ex
@@ -1,3 +1,4 @@
 defmodule Backend.Mailer do
+  @moduledoc false
   use Swoosh.Mailer, otp_app: :backend
 end
diff --git a/backend/lib/mailer/user_email.ex b/backend/lib/mailer/user_email.ex
index a395bbd..51857a8 100644
--- a/backend/lib/mailer/user_email.ex
+++ b/backend/lib/mailer/user_email.ex
@@ -1,4 +1,7 @@
 defmodule Backend.Mailer.UserEmail do
+  @moduledoc """
+  Module for sending emails to users.
+  """
   import Swoosh.Email
   import Backend.{Auth, Util}
   require Logger
diff --git a/backend/lib/mix/tasks/crawl.ex b/backend/lib/mix/tasks/crawl.ex
deleted file mode 100644
index c9495c8..0000000
--- a/backend/lib/mix/tasks/crawl.ex
+++ /dev/null
@@ -1,13 +0,0 @@
-defmodule Mix.Tasks.Crawl do
-  alias Backend.Crawler
-  use Mix.Task
-
-  @shortdoc "Crawl a given instance."
-
-  def run(domain) do
-    Mix.Task.run("app.start")
-    # Application.ensure_all_started(:timex)
-    # Mix.Task.run("loadconfig")
-    Crawler.run(domain)
-  end
-end
diff --git a/backend/mix.exs b/backend/mix.exs
index c86b882..8c19079 100644
--- a/backend/mix.exs
+++ b/backend/mix.exs
@@ -62,7 +62,8 @@ defmodule Backend.MixProject do
       {:swoosh, "~> 0.23.3"},
       {:ex_twilio, "~> 0.7.0"},
       {:elasticsearch, "~> 1.0"},
-      {:appsignal, "~> 1.10.1"}
+      {:appsignal, "~> 1.10.1"},
+      {:credo, "~> 1.1", only: [:dev, :test], runtime: false}
     ]
   end
 
diff --git a/backend/mix.lock b/backend/mix.lock
index f1dab42..04bf223 100644
--- a/backend/mix.lock
+++ b/backend/mix.lock
@@ -2,12 +2,14 @@
   "appsignal": {:hex, :appsignal, "1.10.11", "5df2546d6ea15e392a4384b175ebc1bb33f4ccf8fe9872c11542d3ae2043ff88", [:make, :mix], [{:decorator, "~> 1.2.3", [hex: :decorator, repo: "hexpm", optional: false]}, {:hackney, "~> 1.6", [hex: :hackney, repo: "hexpm", optional: false]}, {:phoenix, ">= 1.2.0", [hex: :phoenix, repo: "hexpm", optional: true]}, {:plug, ">= 1.1.0", [hex: :plug, repo: "hexpm", optional: true]}, {:poison, ">= 1.3.0", [hex: :poison, repo: "hexpm", optional: false]}], "hexpm"},
   "artificery": {:hex, :artificery, "0.4.2", "3ded6e29e13113af52811c72f414d1e88f711410cac1b619ab3a2666bbd7efd4", [:mix], [], "hexpm"},
   "base64url": {:hex, :base64url, "0.0.1", "36a90125f5948e3afd7be97662a1504b934dd5dac78451ca6e9abf85a10286be", [:rebar], [], "hexpm"},
+  "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm"},
   "certifi": {:hex, :certifi, "2.5.1", "867ce347f7c7d78563450a18a6a28a8090331e77fa02380b4a21962a65d36ee5", [:rebar3], [{:parse_trans, "~>3.3", [hex: :parse_trans, repo: "hexpm", optional: false]}], "hexpm"},
   "combine": {:hex, :combine, "0.10.0", "eff8224eeb56498a2af13011d142c5e7997a80c8f5b97c499f84c841032e429f", [:mix], [], "hexpm"},
   "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], [], "hexpm"},
   "corsica": {:hex, :corsica, "1.1.2", "5ad8b9dcbeeda4762d78a57c0c8c2f88e1eef8741508517c98cb79e0db1f107d", [:mix], [{:plug, "~> 1.0", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm"},
   "cowboy": {:hex, :cowboy, "2.6.3", "99aa50e94e685557cad82e704457336a453d4abcb77839ad22dbe71f311fcc06", [:rebar3], [{:cowlib, "~> 2.7.3", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "~> 1.7.1", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm"},
   "cowlib": {:hex, :cowlib, "2.7.3", "a7ffcd0917e6d50b4d5fb28e9e2085a0ceb3c97dea310505f7460ff5ed764ce9", [:rebar3], [], "hexpm"},
+  "credo": {:hex, :credo, "1.1.3", "bf31887b8914a4b7e1810ae2b5aab7c657698abbf4cca6a2335a094d57995168", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm"},
   "crontab": {:hex, :crontab, "1.1.7", "b9219f0bdc8678b94143655a8f229716c5810c0636a4489f98c0956137e53985", [:mix], [{:ecto, "~> 1.0 or ~> 2.0 or ~> 3.0", [hex: :ecto, repo: "hexpm", optional: true]}], "hexpm"},
   "db_connection": {:hex, :db_connection, "2.1.0", "122e2f62c4906bf2e49554f1e64db5030c19229aa40935f33088e7d543aa79d0", [:mix], [{:connection, "~> 1.0.2", [hex: :connection, repo: "hexpm", optional: false]}], "hexpm"},
   "decimal": {:hex, :decimal, "1.8.0", "ca462e0d885f09a1c5a342dbd7c1dcf27ea63548c65a65e67334f4b61803822e", [:mix], [], "hexpm"},
diff --git a/backend/test/support/channel_case.ex b/backend/test/support/channel_case.ex
index 29cb07f..0c84a26 100644
--- a/backend/test/support/channel_case.ex
+++ b/backend/test/support/channel_case.ex
@@ -14,6 +14,7 @@ defmodule BackendWeb.ChannelCase do
   """
 
   use ExUnit.CaseTemplate
+  alias Ecto.Adapters.SQL.Sandbox
 
   using do
     quote do
@@ -26,10 +27,10 @@ defmodule BackendWeb.ChannelCase do
   end
 
   setup tags do
-    :ok = Ecto.Adapters.SQL.Sandbox.checkout(Backend.Repo)
+    :ok = Sandbox.checkout(Backend.Repo)
 
     unless tags[:async] do
-      Ecto.Adapters.SQL.Sandbox.mode(Backend.Repo, {:shared, self()})
+      Sandbox.mode(Backend.Repo, {:shared, self()})
     end
 
     :ok
diff --git a/backend/test/support/conn_case.ex b/backend/test/support/conn_case.ex
index d211e49..270d497 100644
--- a/backend/test/support/conn_case.ex
+++ b/backend/test/support/conn_case.ex
@@ -14,6 +14,7 @@ defmodule BackendWeb.ConnCase do
   """
 
   use ExUnit.CaseTemplate
+  alias Ecto.Adapters.SQL.Sandbox
 
   using do
     quote do
@@ -27,10 +28,10 @@ defmodule BackendWeb.ConnCase do
   end
 
   setup tags do
-    :ok = Ecto.Adapters.SQL.Sandbox.checkout(Backend.Repo)
+    :ok = Sandbox.checkout(Backend.Repo)
 
     unless tags[:async] do
-      Ecto.Adapters.SQL.Sandbox.mode(Backend.Repo, {:shared, self()})
+      Sandbox.mode(Backend.Repo, {:shared, self()})
     end
 
     {:ok, conn: Phoenix.ConnTest.build_conn()}
diff --git a/backend/test/support/data_case.ex b/backend/test/support/data_case.ex
index a073792..2603d09 100644
--- a/backend/test/support/data_case.ex
+++ b/backend/test/support/data_case.ex
@@ -13,6 +13,7 @@ defmodule Backend.DataCase do
   """
 
   use ExUnit.CaseTemplate
+  alias Ecto.Adapters.SQL.Sandbox
 
   using do
     quote do
@@ -26,10 +27,10 @@ defmodule Backend.DataCase do
   end
 
   setup tags do
-    :ok = Ecto.Adapters.SQL.Sandbox.checkout(Backend.Repo)
+    :ok = Sandbox.checkout(Backend.Repo)
 
     unless tags[:async] do
-      Ecto.Adapters.SQL.Sandbox.mode(Backend.Repo, {:shared, self()})
+      Sandbox.mode(Backend.Repo, {:shared, self()})
     end
 
     :ok