diff --git a/.builds/debian-stable.yml b/.builds/debian-stable.yml
index 5b7a7785dbb0cd26edfdd034572e309b82636ef8..c5f9b2338e84c62d19de840c72f98223827112db 100644
--- a/.builds/debian-stable.yml
+++ b/.builds/debian-stable.yml
@@ -6,6 +6,7 @@ packages:
 - ruby-dev
 - bundler
 - libxml2-dev
+- libpq-dev
 - rubocop
 environment:
   LANG: C.UTF-8
diff --git a/.gitignore b/.gitignore
index 9f1b2e43f3d783b484dd367a8a63306c058e35da..0ffb26156a239a949bf9012634f98fa5899ecf3b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,4 @@
 .bundle
 .gems
 Gemfile.lock
-braintree.dhall
\ No newline at end of file
+*.dhall
\ No newline at end of file
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000000000000000000000000000000000000..7b04718ad592e540c6d1679b2607a72bc1c51f4a
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "schemas"]
+	path = schemas
+	url = https://git.singpolyma.net/jmp-schemas
diff --git a/.rubocop.yml b/.rubocop.yml
index 51689e074c871e3eaadf2cb2a2f5b10442a6e455..3f393ef57e08bb0befa746868e21df62110414b8 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,6 +1,10 @@
 Metrics/LineLength:
   Max: 80
 
+Metrics/BlockLength:
+  ExcludedMethods:
+    - route
+
 Layout/Tab:
   Enabled: false
 
diff --git a/Gemfile b/Gemfile
index f5059797f2f35e2dca9d3e10486e888029ebe7af..2ae45b84bafadb0b12b35bb9948a071b18a0319d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,6 +4,7 @@ source "https://rubygems.org"
 
 gem "braintree"
 gem "dhall"
+gem "pg"
 gem "redis"
 gem "roda"
 gem "slim"
diff --git a/config.ru b/config.ru
index 3f9e7dd290dbf0041eedd6eaea1d3a8122645b24..b944b74768a0adb1a26beb3e902ddff3e5eff267 100644
--- a/config.ru
+++ b/config.ru
@@ -3,11 +3,21 @@
 require "braintree"
 require "delegate"
 require "dhall"
+require "pg"
 require "redis"
 require "roda"
 
+require_relative "lib/electrum"
+
 REDIS = Redis.new
 BRAINTREE_CONFIG = Dhall.load("env:BRAINTREE_CONFIG").sync
+ELECTRUM = Electrum.new(
+	**Dhall::Coder.load("env:ELECTRUM_CONFIG", transform_keys: :to_sym)
+)
+
+DB = PG.connect(dbname: "jmp")
+DB.type_map_for_results = PG::BasicTypeMapForResults.new(DB)
+DB.type_map_for_queries = PG::BasicTypeMapForQueries.new(DB)
 
 class CreditCardGateway
 	def initialize(jid, customer_id=nil)
@@ -77,11 +87,67 @@ protected
 	end
 end
 
+class UnknownTransactions
+	def self.from(customer_id, address, tx_hashes)
+		values = tx_hashes.map do |tx_hash|
+			"('#{DB.escape_string(tx_hash)}/#{DB.escape_string(address)}')"
+		end
+		rows = DB.exec_params(<<-SQL)
+			SELECT transaction_id FROM
+				(VALUES #{values.join(',')}) AS t(transaction_id)
+				LEFT JOIN transactions USING (transaction_id)
+			WHERE transactions.transaction_id IS NULL
+		SQL
+		new(customer_id, rows.map { |row| row["transaction_id"] })
+	end
+
+	def initialize(customer_id, transaction_ids)
+		@customer_id = customer_id
+		@transaction_ids = transaction_ids
+	end
+
+	def enqueue!
+		REDIS.hset(
+			"pending_btc_transactions",
+			*@transaction_ids.flat_map { |txid| [txid, @customer_id] }
+		)
+	end
+end
+
 class JmpPay < Roda
 	plugin :render, engine: "slim"
 	plugin :common_logger, $stdout
 
+	def redis_key_btc_addresses
+		"jmp_customer_btc_addresses-#{request.params['customer_id']}"
+	end
+
+	def verify_address_customer_id(r)
+		return if REDIS.sismember(redis_key_btc_addresses, request.params["address"])
+
+		warn "Address and customer_id do not match"
+		r.halt(
+			403,
+			{"Content-Type" => "text/plain"},
+			"Address and customer_id do not match"
+		)
+	end
+
 	route do |r|
+		r.on "electrum_notify" do
+			verify_address_customer_id(r)
+
+			UnknownTransactions.from(
+				request.params["customer_id"],
+				request.params["address"],
+				ELECTRUM
+					.getaddresshistory(request.params["address"])
+					.map { |item| item["tx_hash"] }
+			).enqueue!
+
+			"OK"
+		end
+
 		r.on :jid do |jid|
 			r.on "credit_cards" do
 				gateway = CreditCardGateway.new(
diff --git a/lib/electrum.rb b/lib/electrum.rb
new file mode 100644
index 0000000000000000000000000000000000000000..8a972d5857500659bdcef7a7d3b91725fdcfee3b
--- /dev/null
+++ b/lib/electrum.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "json"
+require "net/http"
+require "securerandom"
+
+class Electrum
+	def initialize(rpc_uri:, rpc_username:, rpc_password:)
+		@rpc_uri = URI(rpc_uri)
+		@rpc_username = rpc_username
+		@rpc_password = rpc_password
+	end
+
+	def getaddresshistory(address)
+		rpc_call(:getaddresshistory, address: address)["result"]
+	end
+
+protected
+
+	def rpc_call(method, params)
+		JSON.parse(post_json(
+			jsonrpc: "2.0",
+			id: SecureRandom.hex,
+			method: method.to_s,
+			params: params
+		).body)
+	end
+
+	def post_json(data)
+		req = Net::HTTP::Post.new(@rpc_uri, "Content-Type" => "application/json")
+		req.basic_auth(@rpc_username, @rpc_password)
+		req.body = data.to_json
+		Net::HTTP.start(
+			@rpc_uri.hostname,
+			@rpc_uri.port,
+			use_ssl: @rpc_uri.scheme == "https"
+		) do |http|
+			http.request(req)
+		end
+	end
+end
diff --git a/schemas b/schemas
new file mode 160000
index 0000000000000000000000000000000000000000..3e0d7e8ae7193f567294036c3235d50ed318b945
--- /dev/null
+++ b/schemas
@@ -0,0 +1 @@
+Subproject commit 3e0d7e8ae7193f567294036c3235d50ed318b945