diff --git a/backend/config/config.exs b/backend/config/config.exs
index be41b33..d652545 100644
--- a/backend/config/config.exs
+++ b/backend/config/config.exs
@@ -18,6 +18,11 @@ config :backend, BackendWeb.Endpoint,
 
 config :backend, Backend.Repo, queue_target: 5000
 
+config :backend, Backend.Elasticsearch.Cluster,
+  url: "http://elastic:9200",
+  api: Elasticsearch.API.HTTP,
+  json_library: Jason
+
 # Configures Elixir's Logger
 config :logger, :console,
   format: "$time $metadata[$level] $message\n",
diff --git a/backend/config/releases.exs b/backend/config/releases.exs
index dfd3c76..bd80c1e 100644
--- a/backend/config/releases.exs
+++ b/backend/config/releases.exs
@@ -14,6 +14,9 @@ config :backend, Backend.Repo,
   pool_size: String.to_integer(System.get_env("POOL_SIZE") || "10"),
   ssl: ssl
 
+config :backend, Backend.Elasticsearch.Cluster,
+  url: System.get_env("ELASTICSEARCH_URL") || "http://localhost:9200"
+
 config :appsignal, :config,
   otp_app: :backend,
   revision: System.get_env("GIT_REV")
diff --git a/backend/lib/backend/api.ex b/backend/lib/backend/api.ex
index 9c6df70..cabd619 100644
--- a/backend/lib/backend/api.ex
+++ b/backend/lib/backend/api.ex
@@ -148,10 +148,78 @@ defmodule Backend.Api do
   end
 
   def search_instances(query, filters, from \\ 0) do
-    # TODO: implement w. postgres FTS
+    page_size = 50
+
+    search_response =
+      Elasticsearch.post(
+        Backend.Elasticsearch.Cluster,
+        "/instances/_search",
+        build_es_query(query, filters, page_size, from)
+      )
+
+    with {:ok, result} <- search_response do
+      hits =
+        get_in(result, ["hits", "hits"])
+        |> Enum.map(fn h -> h |> Map.get("_source") |> convert_keys_to_atoms() end)
+
+      next =
+        if length(hits) < page_size do
+          nil
+        else
+          from + page_size
+        end
+
+      %{
+        hits: hits,
+        next: next
+      }
+    end
+  end
+
+  defp build_es_query(query, filters, page_size, from) do
+    opt_out_filter = %{"term" => %{"opt_out" => "false"}}
+    filters = [opt_out_filter | filters]
+
     %{
-      hits: [],
-      next: nil
+      "sort" => "_score",
+      "from" => from,
+      "size" => page_size,
+      # This must be >0, otherwise all documents will be returned
+      "min_score" => 1,
+      "query" => %{
+        "bool" => %{
+          "filter" => filters,
+          "should" => [
+            %{
+              "multi_match" => %{
+                "query" => query,
+                "fields" => [
+                  "description.*",
+                  "domain.english"
+                ]
+              }
+            },
+            %{
+              # If the query exactly matches a domain, that instance should always be the first result.
+              "wildcard" => %{
+                "domain.keyword" => %{
+                  "value" => query,
+                  "boost" => 100
+                }
+              }
+            },
+            %{
+              # Give substring matches in domains a large boost, too.
+              "wildcard" => %{
+                "domain.keyword" => %{
+                  "value" => "*#{query}*",
+                  "boost" => 10
+                }
+              }
+            }
+          ]
+        }
+      }
     }
   end
 end
diff --git a/backend/lib/backend/application.ex b/backend/lib/backend/application.ex
index 055f6f6..2d8ec13 100644
--- a/backend/lib/backend/application.ex
+++ b/backend/lib/backend/application.ex
@@ -26,6 +26,7 @@ defmodule Backend.Application do
       ),
       Supervisor.child_spec({Task, fn -> HTTPoison.start() end}, id: :start_httpoison),
       Backend.Scheduler,
+      Backend.Elasticsearch.Cluster,
       Graph.Cache
     ]
 
diff --git a/backend/lib/backend/crawler/crawler.ex b/backend/lib/backend/crawler/crawler.ex
index fb21015..9f69866 100644
--- a/backend/lib/backend/crawler/crawler.ex
+++ b/backend/lib/backend/crawler/crawler.ex
@@ -189,6 +189,8 @@ defmodule Backend.Crawler do
       conflict_target: :domain
     )
 
+    Elasticsearch.put_document!(Backend.Elasticsearch.Cluster, instance, "instances/_doc")
+
     ## Save details of a new crawl ##
     curr_crawl =
       Repo.insert!(%Crawl{
diff --git a/backend/lib/backend/elasticsearch/cluster.ex b/backend/lib/backend/elasticsearch/cluster.ex
new file mode 100644
index 0000000..d34a9c8
--- /dev/null
+++ b/backend/lib/backend/elasticsearch/cluster.ex
@@ -0,0 +1,22 @@
+defmodule Backend.Elasticsearch.Cluster do
+  @moduledoc false
+  use Elasticsearch.Cluster, otp_app: :backend
+
+  def init(config) do
+    indexes = %{
+      instances: %{
+        settings: Application.app_dir(:backend, "priv/elasticsearch/instances.json"),
+        store: Backend.Elasticsearch.Store,
+        sources: [Backend.Instance],
+        bulk_page_size: 1000,
+        bulk_wait_interval: 1000
+      }
+    }
+
+    config =
+      config
+      |> Map.put(:indexes, indexes)
+
+    {:ok, config}
+  end
+end
diff --git a/backend/lib/backend/elasticsearch/store.ex b/backend/lib/backend/elasticsearch/store.ex
new file mode 100644
index 0000000..aa5bc98
--- /dev/null
+++ b/backend/lib/backend/elasticsearch/store.ex
@@ -0,0 +1,17 @@
+defmodule Backend.Elasticsearch.Store do
+  @moduledoc false
+  @behaviour Elasticsearch.Store
+
+  alias Backend.Repo
+
+  @impl true
+  def stream(schema) do
+    Repo.stream(schema)
+  end
+
+  @impl true
+  def transaction(fun) do
+    {:ok, result} = Repo.transaction(fun, timeout: :infinity)
+    result
+  end
+end
diff --git a/backend/lib/backend/instance.ex b/backend/lib/backend/instance.ex
index f690e3c..fa351f5 100644
--- a/backend/lib/backend/instance.ex
+++ b/backend/lib/backend/instance.ex
@@ -62,4 +62,20 @@ defmodule Backend.Instance do
     |> validate_required([:domain])
     |> put_assoc(:peers, attrs.peers)
   end
+
+  defimpl Elasticsearch.Document, for: Backend.Instance do
+    def id(instance), do: instance.id
+    def routing(_), do: false
+
+    def encode(instance) do
+      # Make sure this corresponds with priv/elasticseach/instances.json
+      %{
+        domain: instance.domain,
+        description: instance.description,
+        type: instance.type,
+        user_count: instance.user_count,
+        opt_out: instance.opt_out
+      }
+    end
+  end
 end
diff --git a/backend/lib/backend/release.ex b/backend/lib/backend/release.ex
index 7f01eb5..cb5eaaa 100644
--- a/backend/lib/backend/release.ex
+++ b/backend/lib/backend/release.ex
@@ -9,11 +9,20 @@ defmodule Backend.Release do
     :ssl,
     :postgrex,
     :ecto,
+    :elasticsearch,
     @app
   ]
 
+  # Ecto repos to start, if any
+  @repos Application.compile_env(:backend, :ecto_repos, [])
+  # Elasticsearch clusters to start
+  @clusters [Backend.Elasticsearch.Cluster]
+  # Elasticsearch indexes to build
+  @indexes [:instances]
+
   def run_all do
     migrate()
+    build_elasticsearch_indexes()
   end
 
   def migrate do
@@ -26,6 +35,28 @@ defmodule Backend.Release do
     {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
   end
 
+  def build_elasticsearch_indexes do
+    start_services()
+    IO.puts("Building indexes...")
+    Enum.each(@indexes, &Elasticsearch.Index.hot_swap(Backend.Elasticsearch.Cluster, &1))
+    stop_services()
+  end
+
+  # Ensure that all OTP apps, repos used by your Elasticsearch store,
+  # and your Elasticsearch Cluster(s) are started
+  defp start_services do
+    IO.puts("Starting dependencies...")
+    Enum.each(@start_apps, &Application.ensure_all_started/1)
+    IO.puts("Starting repos...")
+    Enum.each(@repos, & &1.start_link(pool_size: 1))
+    IO.puts("Starting clusters...")
+    Enum.each(@clusters, & &1.start_link())
+  end
+
+  defp stop_services do
+    :init.stop()
+  end
+
   defp repos do
     Application.load(@app)
     Application.fetch_env!(@app, :ecto_repos)
diff --git a/backend/lib/backend_web/controllers/admin_controller.ex b/backend/lib/backend_web/controllers/admin_controller.ex
index 276c416..66ff536 100644
--- a/backend/lib/backend_web/controllers/admin_controller.ex
+++ b/backend/lib/backend_web/controllers/admin_controller.ex
@@ -19,6 +19,14 @@ defmodule BackendWeb.AdminController do
     with {:ok, domain} <- Auth.verify_token(token) do
       %{"optIn" => opt_in, "optOut" => opt_out} = params
 
+      # Make sure to update ElasticSearch so that the instance is no longer returned in search results
+      es_instance =
+        Api.get_instance(domain)
+        |> Map.put(:opt_in, opt_in)
+        |> Map.put(:opt_out, opt_out)
+
+      Elasticsearch.put_document!(Backend.Elasticsearch.Cluster, es_instance, "instances")
+
       ecto_instance = %Instance{
         domain: domain,
         opt_in: opt_in,
diff --git a/backend/mix.exs b/backend/mix.exs
index 239270f..1ba757e 100644
--- a/backend/mix.exs
+++ b/backend/mix.exs
@@ -23,6 +23,7 @@ defmodule Backend.MixProject do
         :logger,
         :runtime_tools,
         :gollum,
+        :elasticsearch,
         :appsignal,
         :swoosh,
         :gen_smtp
@@ -63,6 +64,7 @@ defmodule Backend.MixProject do
       {:public_suffix, git: "https://github.com/axelson/publicsuffix-elixir"},
       {:swoosh, "~> 1.0"},
       {:gen_smtp, "~> 1.2"},
+      {:elasticsearch, "~> 1.0"},
       {:appsignal_phoenix, "~> 2.3"},
       {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
       {:nebulex, "~> 2.4.2"},
diff --git a/backend/mix.lock b/backend/mix.lock
index 00e8fd0..b8805b9 100644
--- a/backend/mix.lock
+++ b/backend/mix.lock
@@ -18,6 +18,7 @@
   "decorator": {:hex, :decorator, "1.4.0", "a57ac32c823ea7e4e67f5af56412d12b33274661bb7640ec7fc882f8d23ac419", [:mix], [], "hexpm", "0a07cedd9083da875c7418dea95b78361197cf2bf3211d743f6f7ce39656597f"},
   "ecto": {:hex, :ecto, "3.10.1", "c6757101880e90acc6125b095853176a02da8f1afe056f91f1f90b80c9389822", [:mix], [{:decimal, "~> 1.6 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "d2ac4255f1601bdf7ac74c0ed971102c6829dc158719b94bd30041bbad77f87a"},
   "ecto_sql": {:hex, :ecto_sql, "3.10.1", "6ea6b3036a0b0ca94c2a02613fd9f742614b5cfe494c41af2e6571bb034dd94c", [:mix], [{:db_connection, "~> 2.4.1 or ~> 2.5", [hex: :db_connection, repo: "hexpm", optional: false]}, {:ecto, "~> 3.10.0", [hex: :ecto, repo: "hexpm", optional: false]}, {:myxql, "~> 0.6.0", [hex: :myxql, repo: "hexpm", optional: true]}, {:postgrex, "~> 0.16.0 or ~> 0.17.0 or ~> 1.0", [hex: :postgrex, repo: "hexpm", optional: true]}, {:tds, "~> 2.1.1 or ~> 2.2", [hex: :tds, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4.0 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "f6a25bdbbd695f12c8171eaff0851fa4c8e72eec1e98c7364402dda9ce11c56b"},
+  "elasticsearch": {:hex, :elasticsearch, "1.0.1", "8339538d90af6b280f10ecd02b1eae372f09373e629b336a13461babf7366495", [:mix], [{:httpoison, ">= 0.0.0", [hex: :httpoison, repo: "hexpm", optional: false]}, {:poison, ">= 0.0.0", [hex: :poison, repo: "hexpm", optional: true]}, {:sigaws, "~> 0.7", [hex: :sigaws, repo: "hexpm", optional: true]}, {:vex, "~> 0.6", [hex: :vex, repo: "hexpm", optional: false]}], "hexpm", "83e7d8b8bee3e7e19a06ab4d357d24845ac1da894e79678227fd52c0b7f71867"},
   "ex2ms": {:hex, :ex2ms, "1.6.1", "66d472eb14da43087c156e0396bac3cc7176b4f24590a251db53f84e9a0f5f72", [:mix], [], "hexpm", "a7192899d84af03823a8ec2f306fa858cbcce2c2e7fd0f1c49e05168fb9c740e"},
   "ex_rated": {:hex, :ex_rated, "2.1.0", "d40e6fe35097b10222df2db7bb5dd801d57211bac65f29063de5f201c2a6aebc", [:mix], [{:ex2ms, "~> 1.5", [hex: :ex2ms, repo: "hexpm", optional: false]}], "hexpm", "936c155337253ed6474f06d941999dd3a9cf0fe767ec99a59f2d2989dc2cc13f"},
   "expo": {:hex, :expo, "0.4.1", "1c61d18a5df197dfda38861673d392e642649a9cef7694d2f97a587b2cfb319b", [:mix], [], "hexpm", "2ff7ba7a798c8c543c12550fa0e2cbc81b95d4974c65855d8d15ba7b37a1ce47"},
diff --git a/docker-compose.yaml b/docker-compose.yaml
index 8e70009..b302256 100644
--- a/docker-compose.yaml
+++ b/docker-compose.yaml
@@ -5,22 +5,32 @@ networks:
     external: false
 
 services:
-  web:
-    image: ghcr.io/fediverse-space/fediverse.space:main
+  phoenix:
+    build: backend
     restart: unless-stopped
     networks:
       - space
     depends_on:
       - db
 
+  gephi:
+    build: gephi
+
   db:
     image: postgres:15-alpine
     restart: unless-stopped
     environment:
-      - POSTGRES_PASSWORD=${DB_PASSWORD}
-      - POSTGRES_USER=${DB_USER}
-      - POSTGRES_DB=${DB_NAME}
+      - POSTGRES_PASSWORD=postgres
+      - POSTGRES_USER=postgres
     networks:
       - space
     volumes:
       - /var/lib/postgresql/data
+
+  elastic:
+    image: elasticsearch:8.7.0
+    restart: unless-stopped
+    environment:
+      - discovery.type=single-node
+    networks: 
+      - space
diff --git a/example.env b/example.env
index e2d9579..3ae6590 100644
--- a/example.env
+++ b/example.env
@@ -1,4 +1,4 @@
 DATABASE_URL="postgres://postgres:postgres@localhost:5432/backend_dev"
 PORT=4000
 BACKEND_HOSTNAME=localhost
-SECRET_KEY_BASE=jLqbBjtQTyZj+1yLwDV8xgZYvZKIBx1MBWbcC2a0mZqB5ivYKQ7GOqNR91g6YnR8
+SECRET_KEY_BASE=jLqbBjtQTyZj+1yLwDV8xgZYvZKIBx1MBWbcC2a0mZqB5ivYKQ7GOqNR91g6YnR8
\ No newline at end of file