diff --git a/Makefile b/Makefile
index 42e6dbf..68cd6a1 100644
--- a/Makefile
+++ b/Makefile
@@ -5,9 +5,15 @@ Q ?= @
 SHOULD_UPDATE = ./bin/should-update
 DBDIR=/tmp/tests-on-dodb
 
+RESULTS_DIR=results
 benchmark-cars:
 	$(Q)crystal build spec/benchmark-cars.cr $(OPTS) --release
 
+benchmark-cars-run: benchmark-cars
+	./benchmark-cars search # by default, test search durations
+	./bin/stats.sh $(RESULTS_DIR)
+	./bin/extract-data-benchmark-cars.sh $(RESULTS_DIR)
+
 build: benchmark-cars
 
 wipe-db:
diff --git a/paper/graph_query_partition.grap b/paper/graph_query_partition.grap
index f7d9a65..8bb765d 100644
--- a/paper/graph_query_partition.grap
+++ b/paper/graph_query_partition.grap
@@ -7,8 +7,8 @@ ticks left out from 0 to 350 by 50
 label left "Request duration" unaligned "for a partition (ms)" "(Median)" left 0.8
 label bot "Number of cars matching the partition" down 0.1
 
-obram = obuncache = obcache = obsemi = 0
-cbram = cbuncache = cbcache = cbsemi = 0
+obram = obuncache = obfifo = obcache = obsemi = 0
+cbram = cbuncache = cbfifo = cbcache = cbsemi = 0
 
 legendxleft  = 1000
 legendxright = 6500
@@ -23,21 +23,26 @@ copy "../data/partitions.d" thru X
 
 	y_scale = 1000000
 
-	# ram cached semi uncached
+	# ram cached fifo semi uncached
 	line from cx,$2/y_scale  to cx,$4/y_scale
 	line from cx,$5/y_scale  to cx,$7/y_scale
 	line from cx,$8/y_scale  to cx,$10/y_scale
 	line from cx,$11/y_scale to cx,$13/y_scale
+	line from cx,$14/y_scale to cx,$16/y_scale
 
 	#ty = $3
 
 	cbram     = $3/y_scale
 	cbcache   = $6/y_scale
-	cbsemi    = $9/y_scale
-	cbuncache = $12/y_scale
+	cbfifo    = $9/y_scale
+	cbsemi    = $12/y_scale
+	cbuncache = $15/y_scale
 
 	if (obram > 0) then {line from cx,cbram to ox,obram}
 	if (obcache > 0) then {line from cx,cbcache to ox,obcache}
+.gcolor pink
+	if (obfifo > 0) then {line from cx,cbfifo to ox,obfifo}
+.gcolor
 .gcolor blue
 	if (obsemi > 0) then {line from cx,cbsemi to ox,obsemi}
 .gcolor
@@ -47,15 +52,19 @@ copy "../data/partitions.d" thru X
 
 	obram = cbram
 	obcache = cbcache
+	obfifo = cbfifo
 	obsemi = cbsemi
 	obuncache = cbuncache
 	ox = cx
 
-	# ram cached semi uncached
+	# ram cached fifo semi uncached
 .gcolor red
 	bullet at cx,cbram
 .gcolor
 	bullet at cx,cbcache
+.gcolor pink
+	bullet at cx,cbfifo
+.gcolor
 .gcolor blue
 	bullet at cx,cbsemi
 .gcolor
diff --git a/paper/graph_query_tag.grap b/paper/graph_query_tag.grap
index 84a91a0..d4efd86 100644
--- a/paper/graph_query_tag.grap
+++ b/paper/graph_query_tag.grap
@@ -6,8 +6,8 @@ ticks left out from 0 to 170 by 20
 label left "Request duration" unaligned "for a tag (ms)" "(Median)" left 0.8
 label bot "Number of cars matching the tag" down 0.1
 
-obram = obuncache = obcache = obsemi = 0
-cbram = cbuncache = cbcache = cbsemi = 0
+obram = obuncache = obfifo = obcache = obsemi = 0
+cbram = cbuncache = cbfifo = cbcache = cbsemi = 0
 
 legendxleft  = 200
 legendxright = 3000
@@ -22,21 +22,26 @@ copy "../data/tags.d" thru X
 
 	y_scale = 1000000
 
-	# ram cached semi uncached
+	# ram cached fifo semi uncached
 	line from cx,$2/y_scale  to cx,$4/y_scale
 	line from cx,$5/y_scale  to cx,$7/y_scale
 	line from cx,$8/y_scale  to cx,$10/y_scale
 	line from cx,$11/y_scale to cx,$13/y_scale
+	line from cx,$14/y_scale to cx,$16/y_scale
 
 	#ty = $3
 
 	cbram     = $3/y_scale
 	cbcache   = $6/y_scale
-	cbsemi    = $9/y_scale
-	cbuncache = $12/y_scale
+	cbfifo   = $9/y_scale
+	cbsemi    = $12/y_scale
+	cbuncache = $15/y_scale
 
 	if (obram > 0) then {line from cx,cbram to ox,obram}
 	if (obcache > 0) then {line from cx,cbcache to ox,obcache}
+.gcolor pink
+	if (obfifo > 0) then {line from cx,cbfifo to ox,obfifo}
+.gcolor
 .gcolor blue
 	if (obsemi > 0) then {line from cx,cbsemi to ox,obsemi}
 .gcolor
@@ -46,15 +51,19 @@ copy "../data/tags.d" thru X
 
 	obram = cbram
 	obcache = cbcache
+	obfifo = cbfifo
 	obsemi = cbsemi
 	obuncache = cbuncache
 	ox = cx
 
-	# ram cached semi uncached
+	# ram cached fifo semi uncached
 .gcolor red
 	bullet at cx,cbram
 .gcolor
 	bullet at cx,cbcache
+.gcolor pink
+	bullet at cx,cbfifo
+.gcolor
 .gcolor blue
 	bullet at cx,cbsemi
 .gcolor
diff --git a/paper/legend.grap b/paper/legend.grap
index af31174..3af51b1 100644
--- a/paper/legend.grap
+++ b/paper/legend.grap
@@ -19,7 +19,7 @@ define legend {
 	diffx = xright - xleft
 	diffy = yup - ydown
 
-	hdiff = diffy/4.3
+	hdiff = diffy/5.7
 	cy = yup - (diffy/6)
 	cx = (diffx/20) + xleft
 
@@ -27,6 +27,7 @@ define legend {
 	lendx = cx + diffx/8
 	tstartx = lendx + diffx/20
 
+.ps -2
 	.gcolor red
 	line from lstartx,cy to lendx,cy
 	.gcolor
@@ -35,6 +36,11 @@ define legend {
 	line from lstartx,cy to lendx,cy
 	"Cached db and index" ljust at tstartx,cy
 	cy = cy - hdiff
+	.gcolor pink
+	line from lstartx,cy to lendx,cy
+	.gcolor
+	"FIFO db and cached index" ljust at tstartx,cy
+	cy = cy - hdiff
 	.gcolor blue
 	line from lstartx,cy to lendx,cy
 	.gcolor
@@ -44,4 +50,5 @@ define legend {
 	line from lstartx,cy to lendx,cy
 	.gcolor
 	"Uncached db and index" ljust at tstartx,cy
+.ps +2
 }
diff --git a/spec/benchmark-cars.cr b/spec/benchmark-cars.cr
index eb8ce1f..637cf68 100644
--- a/spec/benchmark-cars.cr
+++ b/spec/benchmark-cars.cr
@@ -13,13 +13,6 @@ require "./db-cars.cr"
 # ENV["NBRUN"]            rescue 100
 # ENV["MAXINDEXES"]       rescue 5_000
 
-class DODB::Storage(V)
-	def empty_db
-		while pop
-		end
-	end
-end
-
 class Context
 	class_property report_dir = "results"
 	class_property max_indexes = 5_000
@@ -85,10 +78,36 @@ def prepare_env(storage, name, s_index, s_partition, s_tags, &)
 	long_operation "removing #{name} data" { storage.rm_storage_dir }
 end
 
-def batch()
+def search_benchmark(storage : DODB::Storage(Car),
+		current_db_size : Int32,
+		name : String,
+		search_name : DODB::Index::Basic(Car),
+		search_color : DODB::Index::Partition(Car),
+		search_keywords : DODB::Index::Tags(Car))
+	name_to_search    = ENV["CARNAME"]    rescue "Corvet-#{(current_db_size/2).to_i}"
+	color_to_search   = ENV["CARCOLOR"]   rescue "red"
+	keyword_to_search = ENV["CARKEYWORD"] rescue "spacious"
+	puts "NEW BATCH: db-size #{current_db_size}, name: '#{name_to_search}', color: '#{color_to_search}', tag: '#{keyword_to_search}'"
+	report(storage, "#{name}_#{current_db_size}_index") do
+		corvet = search_name.get name_to_search
+	end
+	if current_db_size <= Context.max_indexes
+		report(storage, "#{name}_#{current_db_size}_partitions") do
+			corvet = search_color.get? color_to_search
+		end
+		report(storage, "#{name}_#{current_db_size}_tags") do
+			corvet = search_keywords.get? keyword_to_search
+		end
+	else
+		fake_report("#{name}_#{current_db_size}_partitions")
+		fake_report("#{name}_#{current_db_size}_tags")
+	end
+end
+
+def bench_searches()
 	cars_ram      = SPECDB::RAMOnly(Car).new
 	cars_cached   = SPECDB::Cached(Car).new
-	cars_fifo     = DODB::FIFOSpecDataBase(Car).new
+	cars_fifo     = SPECDB::FIFO(Car).new "", 5000 # With only 5_000 entries
 	cars_semi     = SPECDB::Uncached(Car).new "-semi"
 	cars_uncached = SPECDB::Uncached(Car).new
 
@@ -98,32 +117,7 @@ def batch()
 	semi_Sby_name,     semi_Sby_color,     semi_Sby_keywords     = cached_indexes   cars_semi
 	uncached_Sby_name, uncached_Sby_color, uncached_Sby_keywords = uncached_indexes cars_uncached
 
-	fn = ->(storage : DODB::Storage(Car),
-			current_db_size : Int32,
-			name : String,
-			search_name : DODB::Index::Basic(Car),
-			search_color : DODB::Index::Partition(Car),
-			search_keywords : DODB::Index::Tags(Car)) {
-
-		name_to_search    = ENV["CARNAME"]    rescue "Corvet-#{(current_db_size/2).to_i}"
-		color_to_search   = ENV["CARCOLOR"]   rescue "red"
-		keyword_to_search = ENV["CARKEYWORD"] rescue "spacious"
-		puts "NEW BATCH: db-size #{current_db_size}, name: '#{name_to_search}', color: '#{color_to_search}', tag: '#{keyword_to_search}'"
-		report(storage, "#{name}_#{current_db_size}_index") do
-			corvet = search_name.get name_to_search
-		end
-		if current_db_size <= Context.max_indexes
-			report(storage, "#{name}_#{current_db_size}_partitions") do
-				corvet = search_color.get? color_to_search
-			end
-			report(storage, "#{name}_#{current_db_size}_tags") do
-				corvet = search_keywords.get? keyword_to_search
-			end
-		else
-			fake_report("#{name}_#{current_db_size}_partitions")
-			fake_report("#{name}_#{current_db_size}_tags")
-		end
-	}
+	fn = ->search_benchmark(DODB::Storage(Car), Int32, String, DODB::Index::Basic(Car), DODB::Index::Partition(Car), DODB::Index::Tags(Car))
 
 	prepare_env cars_ram,      "ram",      ram_Sby_name,      ram_Sby_color,      ram_Sby_keywords,      &fn
 	prepare_env cars_cached,   "cached",   cached_Sby_name,   cached_Sby_color,   cached_Sby_keywords,   &fn
@@ -143,14 +137,16 @@ def perform_add(storage : DODB::Storage(Car))
 	end
 end
 
-def batch_add()
+def bench_add()
 	cars_ram      = SPECDB::RAMOnly(Car).new
 	cars_cached   = SPECDB::Cached(Car).new
+	cars_fifo     = SPECDB::FIFO(Car).new "", 5_000
 	cars_semi     = SPECDB::Uncached(Car).new "-semi"
 	cars_uncached = SPECDB::Uncached(Car).new
 
 	ram_indexes      cars_ram
 	cached_indexes   cars_cached
+	cached_indexes   cars_fifo
 	cached_indexes   cars_semi
 	uncached_indexes cars_uncached
 
@@ -160,6 +156,9 @@ def batch_add()
 	avr = perform_add(cars_cached)
 	puts "(cached db and indexes) add a value (average on #{Context.nb_run} tries): #{avr}"
 
+	avr = perform_add(cars_fifo)
+	puts "(fifo db and cached indexes) add a value (average on #{Context.nb_run} tries): #{avr}"
+
 	avr = perform_add(cars_semi)
 	puts "(uncached db but cached indexes) add a value (average on #{Context.nb_run} tries): #{avr}"
 
@@ -172,6 +171,22 @@ def batch_add()
 	cars_uncached.rm_storage_dir
 end
 
+def bench_50_shades_of_fifo()
+	cars_fifo1 = SPECDB::FIFO(Car).new "",  1_000
+	cars_fifo5 = SPECDB::FIFO(Car).new "",  5_000
+	cars_fifo10 = SPECDB::FIFO(Car).new "", 10_000
+
+	fifo_Sby_name1,   fifo_Sby_color1,   fifo_Sby_keywords1   = cached_indexes cars_fifo1
+	fifo_Sby_name5,   fifo_Sby_color5,   fifo_Sby_keywords5   = cached_indexes cars_fifo5
+	fifo_Sby_name10,  fifo_Sby_color10,  fifo_Sby_keywords10  = cached_indexes cars_fifo10
+
+	fn = ->search_benchmark(DODB::Storage(Car), Int32, String, DODB::Index::Basic(Car), DODB::Index::Partition(Car), DODB::Index::Tags(Car))
+
+	prepare_env cars_fifo1,     "fifo1",     fifo_Sby_name1,     fifo_Sby_color1,     fifo_Sby_keywords1,     &fn
+	prepare_env cars_fifo5,     "fifo5",     fifo_Sby_name5,     fifo_Sby_color5,     fifo_Sby_keywords5,     &fn
+	prepare_env cars_fifo10,    "fifo10",    fifo_Sby_name10,    fifo_Sby_color10,    fifo_Sby_keywords10,    &fn
+end
+
 ENV["REPORT_DIR"]?.try { |report_dir| Context.report_dir = report_dir }
 Dir.mkdir_p Context.report_dir
 
@@ -187,5 +202,18 @@ pp! Context.to
 pp! Context.incr
 pp! Context.max_indexes
 
-batch
-batch_add
+if ARGV.size == 0
+	puts "Usage: benchmark-cars (fifo|search|add)"
+	exit 0
+end
+
+case ARGV[0]
+when /fifo/
+	bench_50_shades_of_fifo
+when /search/
+	bench_searches
+when /add/
+	bench_add
+else
+	puts "Usage: benchmark-cars (fifo|search|add)"
+end
diff --git a/spec/spec-database.cr b/spec/spec-database.cr
index fc0cbfb..5fd9319 100644
--- a/spec/spec-database.cr
+++ b/spec/spec-database.cr
@@ -24,10 +24,10 @@ class SPECDB::Cached(V) < DODB::Storage::Cached(V)
 	end
 end
 
-class DODB::FIFOSpecDataBase(V) < DODB::Storage::Stacked(V)
+class SPECDB::FIFO(V) < DODB::Storage::Stacked(V)
 	property storage_dir : String
-	def initialize(storage_ext = "", remove_previous_data = true)
-		@storage_dir = "specdb-storage-fifo#{storage_ext}"
+	def initialize(storage_ext = "", @max_entries = 100_000, remove_previous_data = true)
+		@storage_dir = "specdb-storage-fifo-#{@max_entries}#{storage_ext}"
 		::FileUtils.rm_rf storage_dir if remove_previous_data
 		super storage_dir
 	end
diff --git a/src/dodb/storage/cached.cr b/src/dodb/storage/cached.cr
index 86fd660..546f6ff 100644
--- a/src/dodb/storage/cached.cr
+++ b/src/dodb/storage/cached.cr
@@ -73,7 +73,6 @@ class DODB::Storage::Cached(V) < DODB::Storage(V)
 		@data[key] rescue raise MissingEntry.new(key)
 	end
 
-	# :inherit:
 	def []=(key : Int32, value : V)
 		old_value = self.[key]?
 
diff --git a/src/dodb/storage/stacked.cr b/src/dodb/storage/stacked.cr
index 23630c9..6f20256 100644
--- a/src/dodb/storage/stacked.cr
+++ b/src/dodb/storage/stacked.cr
@@ -31,7 +31,6 @@
 # ```
 #
 # NOTE: fast for frequently requested data and requires a stable (and configurable) amount of memory.
-# TODO: not yet implemented.
 class DODB::Storage::Stacked(V) < DODB::Storage::Cached(V)
 	# The *stack* a simple FIFO instance where the key of the requested data is pushed.
 	# In case the number of stored entries exceeds what is allowed, the least recently used entry is removed.
@@ -52,9 +51,35 @@ class DODB::Storage::Stacked(V) < DODB::Storage::Cached(V)
 
 	def [](key : Int32) : V
 		val = @data[key] rescue raise MissingEntry.new(key)
+		push_fifo key
+		val
+	end
+
+	# Assumes new entries are more requested than old ones.
+	def []=(key : Int32, value : V)
+		super key, value
+		push_fifo key
+	end
+
+	# :inherit:
+	#
+	# Assumes new entries are more requested than old ones.
+	def <<(item : V)
+		key = super item
+		push_fifo key
+	end
+
+	def unsafe_delete(key : Int32)
+		@stack.delete key if super key
+	end
+
+	def delete(key : Int32)
+		@stack.delete key if super key
+	end
+
+	private def push_fifo(key : Int32)
 		if entry_to_remove = @stack << key
 			@data.delete entry_to_remove
 		end
-		val
 	end
 end
diff --git a/src/fifo.cr b/src/fifo.cr
index 33b4185..81b7093 100644
--- a/src/fifo.cr
+++ b/src/fifo.cr
@@ -27,11 +27,16 @@ class FIFO(V)
 	end
 
 	# Pushes a value in the FIFO and gets the oldest value whether it exceeds the allowed number of entries.
-	# NOTE: `#<<(v : V)` is the only function since it's enough for the intended use, feel free to improve this.
+	# NOTE: `#<<(v : V)` is (almost) the only function since it's enough for the intended use, feel free to improve this.
 	# WARNING: implementation is extremely simple (3 lines) and not designed to be highly efficient.
 	def <<(v : V) : V?
 		@data.select! { |x| v != v }            # remove dups
 		@data.unshift v                         # push on top of the stack
 		@data.pop if @data.size > @max_entries  # remove least recently used entry if `@data` is too big
 	end
+
+	# Removes a value.
+	def delete(v : V)
+		@data.select! { |x| v != v }
+	end
 end