diff --git a/redis/acknowledge.lua b/redis/acknowledge.lua
index 2da9f6e7..e484f378 100644
--- a/redis/acknowledge.lua
+++ b/redis/acknowledge.lua
@@ -3,7 +3,12 @@ local processed_key = KEYS[2]
 local owners_key = KEYS[3]
 
 local test = ARGV[1]
+local ttl = ARGV[2]
 
 redis.call('zrem', zset_key, test)
 redis.call('hdel', owners_key, test)  -- Doesn't matter if it was reclaimed by another workers
-return redis.call('sadd', processed_key, test)
+local acknowledged = redis.call('sadd', processed_key, test)
+
+redis.call('expire', processed_key, ttl)
+
+return acknowledged
diff --git a/redis/heartbeat.lua b/redis/heartbeat.lua
index 6c9c1e9d..730c1ba7 100644
--- a/redis/heartbeat.lua
+++ b/redis/heartbeat.lua
@@ -5,6 +5,7 @@ local worker_queue_key = KEYS[4]
 
 local current_time = ARGV[1]
 local test = ARGV[2]
+local ttl = ARGV[3]
 
 -- already processed, we do not need to bump the timestamp
 if redis.call('sismember', processed_key, test) == 1 then
@@ -13,5 +14,7 @@ end
 
 -- we're still the owner of the test, we can bump the timestamp
 if redis.call('hget', owners_key, test) == worker_queue_key then
-  return redis.call('zadd', zset_key, current_time, test)
+  local result = redis.call('zadd', zset_key, current_time, test)
+  redis.call('expire', zset_key, ttl)
+  return result
 end
diff --git a/redis/release.lua b/redis/release.lua
index 4bcc5929..7e1ed218 100644
--- a/redis/release.lua
+++ b/redis/release.lua
@@ -2,12 +2,15 @@ local zset_key = KEYS[1]
 local worker_queue_key = KEYS[2]
 local owners_key = KEYS[3]
 
+local ttl = ARGV[1]
+
 -- owned_tests = {"SomeTest", "worker:1", "SomeOtherTest", "worker:2", ...}
 local owned_tests = redis.call('hgetall', owners_key)
 for index, owner_or_test in ipairs(owned_tests) do
   if owner_or_test == worker_queue_key then -- If we owned a test
     local test = owned_tests[index - 1]
     redis.call('zadd', zset_key, "0", test) -- We expire the lease immediately
+    redis.call('expire', zset_key, ttl)
     return nil
   end
 end
diff --git a/redis/requeue.lua b/redis/requeue.lua
index a1fcc25c..91e6cc69 100644
--- a/redis/requeue.lua
+++ b/redis/requeue.lua
@@ -9,6 +9,7 @@ local max_requeues = tonumber(ARGV[1])
 local global_max_requeues = tonumber(ARGV[2])
 local test = ARGV[3]
 local offset = ARGV[4]
+local ttl = ARGV[5]
 
 if redis.call('hget', owners_key, test) == worker_queue_key then
    redis.call('hdel', owners_key, test)
@@ -30,6 +31,7 @@ end
 
 redis.call('hincrby', requeues_count_key, '___total___', 1)
 redis.call('hincrby', requeues_count_key, test, 1)
+redis.call('expire', requeues_count_key, ttl)
 
 local pivot = redis.call('lrange', queue_key, -1 - offset, 0 - offset)[1]
 if pivot then
@@ -38,6 +40,7 @@ else
   redis.call('lpush', queue_key, test)
 end
 
+redis.call('expire', queue_key, ttl)
 redis.call('zrem', zset_key, test)
 
 return true
diff --git a/redis/reserve.lua b/redis/reserve.lua
index d5951146..187ee910 100644
--- a/redis/reserve.lua
+++ b/redis/reserve.lua
@@ -5,12 +5,21 @@ local worker_queue_key = KEYS[4]
 local owners_key = KEYS[5]
 
 local current_time = ARGV[1]
+local ttl = ARGV[2]
 
 local test = redis.call('rpop', queue_key)
 if test then
   redis.call('zadd', zset_key, current_time, test)
   redis.call('lpush', worker_queue_key, test)
   redis.call('hset', owners_key, test, worker_queue_key)
+
+  -- Expire at write time. These keys used to rely on an EXPIRE at the tail of
+  -- CI::Queue::Redis::Worker#poll, which never runs for a worker that is killed,
+  -- cancelled, OOMs or loses its Redis connection -- leaking the key forever.
+  redis.call('expire', zset_key, ttl)
+  redis.call('expire', worker_queue_key, ttl)
+  redis.call('expire', owners_key, ttl)
+
   return test
 else
   return nil
diff --git a/redis/reserve_lost.lua b/redis/reserve_lost.lua
index 9dfaa616..c33ca049 100644
--- a/redis/reserve_lost.lua
+++ b/redis/reserve_lost.lua
@@ -5,6 +5,7 @@ local owners_key = KEYS[4]
 
 local current_time = ARGV[1]
 local timeout = ARGV[2]
+local ttl = ARGV[3]
 
 local lost_tests = redis.call('zrangebyscore', zset_key, 0, current_time - timeout)
 for _, test in ipairs(lost_tests) do
@@ -12,6 +13,11 @@ for _, test in ipairs(lost_tests) do
     redis.call('zadd', zset_key, current_time, test)
     redis.call('lpush', worker_queue_key, test)
     redis.call('hset', owners_key, test, worker_queue_key) -- Take ownership
+
+    redis.call('expire', zset_key, ttl)
+    redis.call('expire', worker_queue_key, ttl)
+    redis.call('expire', owners_key, ttl)
+
     return test
   end
 end
diff --git a/ruby/lib/ci/queue/redis/base.rb b/ruby/lib/ci/queue/redis/base.rb
index 9f42c919..31d2d4e8 100644
--- a/ruby/lib/ci/queue/redis/base.rb
+++ b/ruby/lib/ci/queue/redis/base.rb
@@ -118,7 +118,10 @@ def expired?
         end
 
         def created_at=(timestamp)
-          redis.setnx(key('created-at'), timestamp)
+          redis.pipelined do |pipeline|
+            pipeline.setnx(key('created-at'), timestamp)
+            pipeline.expire(key('created-at'), config.redis_ttl)
+          end
         end
 
         def size
@@ -182,7 +185,10 @@ def queue_initializing?
         end
 
         def increment_test_failed
-          redis.incr(key('test_failed_count'))
+          redis.pipelined do |pipeline|
+            pipeline.incr(key('test_failed_count'))
+            pipeline.expire(key('test_failed_count'), config.redis_ttl)
+          end
         end
 
         def test_failed
@@ -241,7 +247,8 @@ def read_script(name)
         end
 
         class HeartbeatProcess
-          def initialize(redis_url, zset_key, processed_key, owners_key, worker_queue_key)
+          def initialize(redis_url, zset_key, processed_key, owners_key, worker_queue_key, redis_ttl)
+            @redis_ttl = redis_ttl
             @redis_url = redis_url
             @zset_key = zset_key
             @processed_key = processed_key
@@ -261,6 +268,7 @@ def boot!
               @processed_key,
               @owners_key,
               @worker_queue_key,
+              @redis_ttl.to_s,
               in: child_read,
               out: child_write,
             )
@@ -335,6 +343,7 @@ def heartbeat_process
             key('processed'),
             key('owners'),
             key('worker', worker_id, 'queue'),
+            config.redis_ttl,
           )
         end
 
diff --git a/ruby/lib/ci/queue/redis/build_record.rb b/ruby/lib/ci/queue/redis/build_record.rb
index b1329ff9..75f0946b 100644
--- a/ruby/lib/ci/queue/redis/build_record.rb
+++ b/ruby/lib/ci/queue/redis/build_record.rb
@@ -53,7 +53,10 @@ def pop_warnings
         end
 
         def record_warning(type, attributes)
-          redis.rpush(key('warnings'), Marshal.dump([type, attributes]))
+          redis.pipelined do |pipeline|
+            pipeline.rpush(key('warnings'), Marshal.dump([type, attributes]))
+            pipeline.expire(key('warnings'), config.redis_ttl)
+          end
         end
 
         def record_error(id, payload, stats: nil)
diff --git a/ruby/lib/ci/queue/redis/monitor.rb b/ruby/lib/ci/queue/redis/monitor.rb
index bdf1466e..56ec6c4e 100755
--- a/ruby/lib/ci/queue/redis/monitor.rb
+++ b/ruby/lib/ci/queue/redis/monitor.rb
@@ -13,7 +13,8 @@ class Monitor
         DEV_SCRIPTS_ROOT = ::File.expand_path('../../../../../../redis', __FILE__)
         RELEASE_SCRIPTS_ROOT = ::File.expand_path('../../redis', __FILE__)
 
-        def initialize(pipe, logger, redis_url, zset_key, processed_key, owners_key, worker_queue_key)
+        def initialize(pipe, logger, redis_url, zset_key, processed_key, owners_key, worker_queue_key, redis_ttl)
+          @redis_ttl = redis_ttl
           @zset_key = zset_key
           @processed_key = processed_key
           @owners_key = owners_key
@@ -40,7 +41,7 @@ def process_tick!(id:)
           eval_script(
             :heartbeat,
             keys: [@zset_key, @processed_key, @owners_key, @worker_queue_key],
-            argv: [Time.now.to_f, id]
+            argv: [Time.now.to_f, id, @redis_ttl]
           )
         rescue => error
           @logger.info(error)
@@ -142,9 +143,10 @@ def monitor
 processed_key = ARGV[2]
 owners_key = ARGV[3]
 worker_queue_key = ARGV[4]
+redis_ttl = ARGV[5]
 
 logger.debug("Starting monitor: #{redis_url} #{zset_key} #{processed_key}")
-manager = CI::Queue::Redis::Monitor.new($stdin, logger, redis_url, zset_key, processed_key, owners_key, worker_queue_key)
+manager = CI::Queue::Redis::Monitor.new($stdin, logger, redis_url, zset_key, processed_key, owners_key, worker_queue_key, redis_ttl)
 
 # Notify the parent we're ready
 $stdout.puts(".")
diff --git a/ruby/lib/ci/queue/redis/worker.rb b/ruby/lib/ci/queue/redis/worker.rb
index c5eb5448..702cee8a 100644
--- a/ruby/lib/ci/queue/redis/worker.rb
+++ b/ruby/lib/ci/queue/redis/worker.rb
@@ -103,7 +103,7 @@ def acknowledge(test)
           eval_script(
             :acknowledge,
             keys: [key('running'), key('processed'), key('owners')],
-            argv: [test_key],
+            argv: [test_key, config.redis_ttl],
           ) == 1
         end
 
@@ -122,7 +122,7 @@ def requeue(test, offset: Redis.requeue_offset)
               key('worker', worker_id, 'queue'),
               key('owners'),
             ],
-            argv: [config.max_requeues, global_max_requeues, test_key, offset],
+            argv: [config.max_requeues, global_max_requeues, test_key, offset, config.redis_ttl],
           ) == 1
 
           @reserved_test = test_key unless requeued
@@ -133,7 +133,7 @@ def release!
           eval_script(
             :release,
             keys: [key('running'), key('worker', worker_id, 'queue'), key('owners')],
-            argv: [],
+            argv: [config.redis_ttl],
           )
           nil
         end
@@ -173,7 +173,7 @@ def try_to_reserve_test
               key('worker', worker_id, 'queue'),
               key('owners'),
             ],
-            argv: [CI::Queue.time_now.to_f],
+            argv: [CI::Queue.time_now.to_f, config.redis_ttl],
           )
         end
 
@@ -188,7 +188,7 @@ def try_to_reserve_lost_test
               key('worker', worker_id, 'queue'),
               key('owners'),
             ],
-            argv: [CI::Queue.time_now.to_f, timeout],
+            argv: [CI::Queue.time_now.to_f, timeout, config.redis_ttl],
           )
 
           if lost_test
diff --git a/ruby/lib/rspec/queue.rb b/ruby/lib/rspec/queue.rb
index 97616058..b60079cf 100644
--- a/ruby/lib/rspec/queue.rb
+++ b/ruby/lib/rspec/queue.rb
@@ -299,14 +299,33 @@ def call(options, stdout, stderr)
 
         step("Waiting for workers to complete")
 
-        unless supervisor.wait_for_workers
-          unless supervisor.queue_initialized?
-            abort! "No master was elected. Did all workers crash?"
+        begin
+          unless supervisor.wait_for_workers
+            unless supervisor.queue_initialized?
+              abort! "No master was elected. Did all workers crash?"
+            end
+
+            unless supervisor.exhausted?
+              abort! "#{supervisor.size} tests weren't run."
+            end
+          end
+
+          # PE-3857: an evicted queue is indistinguishable from a completed one --
+          # the queue reads as exhausted and the error-report hash reads as empty,
+          # so we would report success for a run whose results we no longer have.
+          # Refuse to certify a build whose bookkeeping is gone.
+          total = supervisor.total
+          progress = supervisor.build.progress
+
+          if total.zero?
+            abort! queue_vanished_message("`total` is 0 -- the queue is empty or was never populated")
           end
 
-          unless supervisor.exhausted?
-            abort! "#{supervisor.size} tests weren't run."
+          if progress <= 0
+            abort! queue_vanished_message("no test progress was recorded (total=#{total}, progress=#{progress})")
           end
+        rescue CI::Queue::Redis::LostMaster
+          abort! queue_vanished_message("the master worker record is gone")
         end
 
         # TODO: better reporting
@@ -324,6 +343,13 @@ def call(options, stdout, stderr)
 
       private
 
+      def queue_vanished_message(detail)
+        "Refusing to report a result: #{detail}.\n" \
+          "The queue's Redis keys are missing, so this run cannot be certified as passing. " \
+          "This is not a test failure -- it usually means the keys were evicted (check the " \
+          "ci-queue Redis memory usage) or the build ran longer than CI_QUEUE_REDIS_TTL."
+      end
+
       attr_reader :configuration
 
       def setup(options, out, err)
diff --git a/ruby/test/ci/queue/redis_test.rb b/ruby/test/ci/queue/redis_test.rb
index 5c5bd139..8c1e4b7c 100644
--- a/ruby/test/ci/queue/redis_test.rb
+++ b/ruby/test/ci/queue/redis_test.rb
@@ -270,8 +270,47 @@ def test_initialise_from_rediss_uri
     assert_instance_of CI::Queue::Redis::Worker, queue
   end
 
+  # PE-3857: every key ci-queue writes must carry a TTL at write time.
+  #
+  # These keys used to get their EXPIRE at the tail of Worker#poll, which never
+  # runs for a worker that is killed, cancelled, OOMs or loses its Redis
+  # connection -- so the key leaked forever. On tools-redis-001 that grew to
+  # 464k permanent keys / 9.5 GiB, which then forced the node to evict the live
+  # queue keys of in-flight builds under its volatile-lru policy.
+  #
+  # Deliberately drives reserve/requeue/acknowledge by hand rather than through
+  # #poll, so that the end-of-poll EXPIRE never runs -- that is the leak.
+  def test_every_build_key_has_a_ttl
+    ttl = 600
+    # setup already populated a queue under the same build id with the default
+    # 8h TTL; start clean so this test only measures its own writes.
+    @redis.flushdb
+    queue = worker(1, max_requeues: 1, requeue_tolerance: 1.0, redis_ttl: ttl)
+
+    first = test_for(queue.send(:reserve))
+    queue.requeue(first)
+    second = test_for(queue.send(:reserve))
+    queue.acknowledge(second)
+
+    queue.build.record_warning(:some_warning, test: 'x', timeout: 1)
+    queue.increment_test_failed
+    queue.created_at = CI::Queue.time_now.to_f
+    queue.release!
+
+    keys = @redis.keys('build:*')
+    refute_empty keys
+
+    without_ttl = keys.reject { |key| @redis.ttl(key) > 0 }.sort
+    assert_equal [], without_ttl, "keys written without a TTL: #{without_ttl.join(', ')}"
+    assert keys.all? { |key| @redis.ttl(key) <= ttl }
+  end
+
   private
 
+  def test_for(id)
+    TEST_LIST.find { |test| test.id == id } or raise "unknown test id #{id.inspect}"
+  end
+
   def shuffled_test_list
     CI::Queue.shuffle(TEST_LIST, Random.new(0)).freeze
   end