diff --git a/.dockerignore b/.dockerignore
index 2c72a5f..17fc17c 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,5 +1,6 @@
 .dockerignore
 .DS_Store
+.env
 .git*
 .gitignore
 docker-compose*
diff --git a/.gitignore b/.gitignore
index fd5106f..0baf78e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 .DS_STORE
+.env
+app.rb
diff --git a/Gemfile b/Gemfile
index 116cd7f..4d7b858 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,8 +2,12 @@
 
 source "https://rubygems.org"
 
+gem "octokit", "~> 10.0"
 gem "puma"
 gem "rack-test"
 gem "rackup"
 gem "rspec"
+gem "sinatra-contrib", "~> 4.1"
 gem "sinatra"
+
+gem "pry", "~> 0.15.2", :group => :development
diff --git a/Gemfile.lock b/Gemfile.lock
index 7506843..a631956 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,12 +1,33 @@
 GEM
   remote: https://rubygems.org/
   specs:
+    addressable (2.8.7)
+      public_suffix (>= 2.0.2, < 7.0)
     base64 (0.3.0)
+    coderay (1.1.3)
     diff-lcs (1.6.2)
+    faraday (2.13.4)
+      faraday-net_http (>= 2.0, < 3.5)
+      json
+      logger
+    faraday-net_http (3.4.1)
+      net-http (>= 0.5.0)
+    json (2.13.2)
     logger (1.7.0)
+    method_source (1.1.0)
+    multi_json (1.17.0)
     mustermann (3.0.4)
       ruby2_keywords (~> 0.0.1)
+    net-http (0.6.0)
+      uri
     nio4r (2.7.4)
+    octokit (10.0.0)
+      faraday (>= 1, < 3)
+      sawyer (~> 0.9)
+    pry (0.15.2)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    public_suffix (6.0.2)
     puma (6.6.1)
       nio4r (~> 2.0)
     rack (3.2.0)
@@ -35,6 +56,9 @@ GEM
       rspec-support (~> 3.13.0)
     rspec-support (3.13.5)
     ruby2_keywords (0.0.5)
+    sawyer (0.9.2)
+      addressable (>= 2.3.5)
+      faraday (>= 0.17.3, < 3)
     sinatra (4.1.1)
       logger (>= 1.6.0)
       mustermann (~> 3.0)
@@ -42,18 +66,28 @@ GEM
       rack-protection (= 4.1.1)
       rack-session (>= 2.0.0, < 3)
       tilt (~> 2.0)
+    sinatra-contrib (4.1.1)
+      multi_json (>= 0.0.2)
+      mustermann (~> 3.0)
+      rack-protection (= 4.1.1)
+      sinatra (= 4.1.1)
+      tilt (~> 2.0)
     tilt (2.6.1)
+    uri (1.0.3)
 
 PLATFORMS
   aarch64-linux
   ruby
 
 DEPENDENCIES
+  octokit (~> 10.0)
+  pry (~> 0.15.2)
   puma
   rack-test
   rackup
   rspec
   sinatra
+  sinatra-contrib (~> 4.1)
 
 BUNDLED WITH
-   2.6.9
+   2.6.5
diff --git a/app.rb b/app.rb
index 0651bdf..c850917 100644
--- a/app.rb
+++ b/app.rb
@@ -1,5 +1,60 @@
+require 'date'
+require 'octokit'
 require 'sinatra'
+require 'sinatra/json'
+
+configure :development do
+  set :logging, Logger::DEBUG
+  set :server_settings, timeout: 60
+end
+
+def has_permatag?(version, permatags)
+  (version['metadata']['container']['tags'] & permatags).any?
+end
+
+def younger_than?(version, days_old)
+  cutoff = Time.now - 60*60*24*days_old
+  version['created_at'] > cutoff
+end
+
+github = Octokit::Client.new(per_page: 100, auto_paginate: true)
 
 get '/' do
-  "Hello, world!"
+  'Hello, world!'
+end
+
+# Returns all container packages along with their pruning status, i.e. whether they can/can't be pruned and why
+get '/images' do
+  packages = github.get('orgs/BerkeleyLibrary/packages', {package_type: :container})
+  logger.info "Scanning #{packages.size} packages for prunable images: #{packages.collect(&:name).sort}"
+
+  prunables = [].tap do |sofar|
+    packages.each do |pkg|
+      logger.info "Determining prunable images for #{pkg.name}"
+
+      next unless pkg.repository
+
+      permatags = %w(latest edge)
+      permatags += github.branches(pkg.repository.full_name).collect(&:name)
+      permatags += github.tags(pkg.repository.full_name).collect(&:name)
+
+      github.get("orgs/#{pkg.owner.login}/packages/#{pkg.package_type}/#{pkg.name}/versions").each do |image|
+        if has_permatag? image, permatags
+          pruning_status = :permatagged
+        elsif younger_than? image, 7
+          pruning_status = :recent
+        else
+          pruning_status = :prunable
+        end
+
+        sofar << {
+          image: image.to_attrs,
+          pruning_status: pruning_status,
+          can_be_pruned: pruning_status == :prunable,
+        }
+      end
+    end
+  end
+
+  json prunables
 end
diff --git a/docker-compose.ci.yml b/docker-compose.ci.yml
index 9f04aa0..3305ff2 100644
--- a/docker-compose.ci.yml
+++ b/docker-compose.ci.yml
@@ -4,6 +4,7 @@ services:
   app:
     build: !reset
     image: ${DOCKER_APP_IMAGE}
+    env_file: !reset
     ports: !reset
     volumes: !override
       - $ARTIFACTS_DIR:/tmp/artifacts
diff --git a/docker-compose.yml b/docker-compose.yml
index c504ee5..aa1016d 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -3,7 +3,13 @@
 services:
   app:
     build: .
+    env_file:
+      - .env
     ports:
       - 4567:4567
     volumes:
       - ./:/opt/app
+    develop:
+      watch:
+       - action: rebuild
+         path: .