Six and a half ridiculous things to do with Quarkus

Let’s abuse the tools! Everyone knows Quarkus is computationally efficient, expressive, and rock-solid for production.
But did you know that we can use Quarkus efficiency to build applications that shouldn’t go anywhere *near* production?
In this demo-driven session, Holly will put the joy into “developer joy”. She’ll show you all sorts of things you can do
with Quarkus that you probably shouldn’t:

- Build an LLM-powered app that’s *guaranteed* to hallucinate, because you can do more than you think with guardrails,
and truth is so boring

- Write your business code in rockstarlang, because everything should be a hair metal ballad

- Use Minecraft as your observability client, because the LGTM stack doesn’t have enough explosions

- Write a CLI for generating memes faster, because everything is better on the command-line

- Benchmark an application against a grapefruit, because metric units aren’t tasty

Business value? Learning? If you insist. As well as absurd demos, you’ll leave this session with a deeper understanding
of how to get the most out of Quarkus and Java. There will be new Java 25 language features, Quarkus best practices,
powerful integrations, and nifty use cases alongside the silly explosions and grapefruit.

Transcript

1. 6 ½ ridiculous things to do with Quarkus Holly Cummins IBM
3. quarkus is used in production by:
4. quarkus is used in production by: • telcos
5. quarkus is used in production by: • telcos • retailers
6. quarkus is used in production by: • telcos • retailers • banks
7. quarkus is used in production by: • telcos • retailers • banks BORING!
8. how quick can quarkus go? 1
9. how quick can quarkus go? 1
10. thanks to markus eisele for the graphics code https://github.com/holly-cummins/meme-generator
11. was this an easy demo?
12. was this an easy demo?
13. was this an easy demo? -writing the cli was easy -native compilation was easy -native compilation + awt + mac is very hard
15. tell your boss you learned … •picocli + quarkus is cool •native is clever tech •…but native has dragons •only go native if you actually need it
16. is quarkus fast? (again) 2
17. is quarkus efficient? 2
19. it’s also about energy
20. it’s also about hardware
21. … hardware and energy are money
22. … hardware and energy are money BORING!
27. 9000 potatoes
28. 0.0007 W
30. t3.nano (minimum quarkus requirement) t3.small 2x t3.small (minimum spring boot requirement) Watts per hour 12.5 14 28
31. t3.nano t3.small 2x t3.small Watts per hour 12.5 14 28 Lemons per hour 17,857 20,000 40,000
32. spring boot 40,000 lemons/hour quarkus 17,857 lemons/hour
34. https://github.com/quarkusio/spring-quarkus-perf-comparison
35. here’s what we see in our controlled lab https://github.com/quarkusio/benchmarks
36. here’s what we see in our controlled lab https://github.com/quarkusio/benchmarks
37. here’s what we see in our controlled lab https://github.com/quarkusio/benchmarks
38. here’s what we see in our controlled lab https://github.com/quarkusio/benchmarks
39. tell your boss you learned … -quarkus uses 2 - 3x fewer compute resources than spring -quarkus is 2 - 3x cheaper to run than spring
40. was this an easy demo?
41. was this an easy demo?
42. was this an easy demo? -bringing 77,857 lemons to amsterdam was too hard
43. was this an easy demo? -bringing 77,857 lemons to amsterdam was too hard -our industry is still learning how to do energy measurement
44. don’t do perf testing on a laptop don’t drive load from the machine being measured
45. 1 67
46. https://github.com/holly-cummins/gen-alpha-iser
47. was this an easy demo?
48. was this an easy demo? super easy
49. tell your boss you learned … @ServerResponseFilter
50. 1 4
51. https://github.com/phillip-kruger/quarkus-jokes
52. was this an easy demo?
53. was this an easy demo? yes, phillip krüger wrote all of it :)
54. tell your boss you learned … the dev ui now has assistants to help you write + debug code
63. https://github.com/quarkiverse/quarkus-bon-jova-rockstar
64. https://github.com/quarkiverse/quarkus-bon-jova-rockstar
65. was this an easy demo?
66. was this an easy demo?
67. was this an easy demo? -friends don’t let friends write compilers
68. was this an easy demo? -friends don’t let friends write compilers -bytecode generation :(
69. was this an easy demo? -friends don’t let friends write compilers -bytecode generation :( -parsing :( :(
70. tell your boss you learned … -the quarkiverse is very welcoming to new extensions -writing a compiler is a bad idea (but if you do go there, use antlr)
71. observability 6½
73. user code
74. user code quarkus framework
75. application user code quarkus framework
76. application user code quarkus framework extensions
77. application user code quarkus framework extensions
78. application user code quarkus framework client extensions
79. application user code quarkus framework client extensions
80. application user code quarkus framework client extensions
81. application user code quarkus framework client extensions
82. application user code quarkus framework client extensions observability stack
83. application user code quarkus framework client metrics extensions observability stack
84. application user code quarkus framework client metrics traces extensions observability stack
85. application user code quarkus framework client metrics traces logs extensions observability stack
86. application user code quarkus framework observability client client metrics traces logs extensions observability stack
87. application user code quarkus framework observability client client metrics traces logs extensions observability stack
88. application user code quarkus framework observability client client dev service (testcontainers) extensions observability stack
89. application user code quarkus framework observability client client dev service (testcontainers) extensions observability stack BORING!
90. application user code quarkus framework client extensions
91. application user code quarkus framework client extensions
92. application user code quarkus framework client extensions minecraft server
93. application user code quarkus framework minecraft client client extensions minecraft server
94. application user code quarkus framework minecraft client client extensions minecraft server
95. application user code quarkus framework minecraft client client extensions minecraft server mod
96. application user code quarkus framework minecraft client client dev service (testcontainers) extensions minecraft server mod
98. https://github.com/quarkiverse/quarkus-observability-minecraft
100. tell your boss you learned … -you can do a lot with interceptors -dev services are awesome
102. https://github.com/quarkiverse/quarkus-observability-minecraft
103. https://github.com/quarkiverse/quarkus-observability-minecraft
104. was this an easy demo?
105. was this an easy demo?
106. was this an easy demo? -extension was easy, minecraft mod was hard
107. was this an easy demo? -extension was easy, minecraft mod was hard -minecraft APIs
108. was this an easy demo? -extension was easy, minecraft mod was hard -minecraft APIs -lack documentation
109. was this an easy demo? -extension was easy, minecraft mod was hard -minecraft APIs -lack documentation -change between minor versions
110. was this an easy demo? -extension was easy, minecraft mod was hard -minecraft APIs -lack documentation -change between minor versions -client-server sync of injected behaviour is hard
111. tell your boss you learned … - typesafe objects are better than a chat box - … but small models may struggle with structured data - gen ai adds latency
112. gen ai: what could possibly go wrong? 4
114. https://www.computerworld.com/article/4059383/openai-admits-ai-hallucinations-are-mathematically-inevitable-not-just-engineering-flaws.html rate of hallucination when summarizing public information:
115. o1: 16% https://www.computerworld.com/article/4059383/openai-admits-ai-hallucinations-are-mathematically-inevitable-not-just-engineering-flaws.html rate of hallucination when summarizing public information:
116. o1: 16% o3: 33% https://www.computerworld.com/article/4059383/openai-admits-ai-hallucinations-are-mathematically-inevitable-not-just-engineering-flaws.html rate of hallucination when summarizing public information:
117. o1: 16% o3: 33% o4-mini: 48% https://www.computerworld.com/article/4059383/openai-admits-ai-hallucinations-are-mathematically-inevitable-not-just-engineering-flaws.html rate of hallucination when summarizing public information:
118. solution: guardrails
119. “LLM-as-a-judge”
120. “LLM-as-a-judge” BORING!
122. was this an easy demo?
123. was this an easy demo?
124. was this an easy demo? -adding guardrails is simple
125. was this an easy demo? -adding guardrails is simple -but … the demo needed
126. was this an easy demo? -adding guardrails is simple -but … the demo needed -a prompt the llm would hallucinate about 50% of the time
127. was this an easy demo? -adding guardrails is simple -but … the demo needed -a prompt the llm would hallucinate about 50% of the time -a reliable guardrail
128. disclaimer: just based on anecdotal experience of local models
129. tell your boss you learned … -guardrails are important - llm-as-a-judge is still an llm -manage context wisely - context cruft lowers response quality - context growth can cause problems
130. what have we done?
131. what have we done? 1. made memes with a cli
132. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources
133. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources 3. translated output with a fi lter
134. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources 3. translated output with a fi lter 4. transformed code with an extension
135. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources 3. translated output with a fi lter 4. transformed code with an extension 5. compiled rock ballads to bytecode
136. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources 3. translated output with a fi lter 4. transformed code with an extension 5. compiled rock ballads to bytecode 6. used minecraft as an observability client
137. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources 3. translated output with a fi lter 4. transformed code with an extension 5. compiled rock ballads to bytecode 6. used minecraft as an observability client 7. ampli fi ed hallucinations
138. what have we done? 1. made memes with a cli 2. con fi rmed quarkus does a lot with very few resources 3. translated output with a fi lter 4. transformed code with an extension 5. compiled rock ballads to bytecode 6. used minecraft as an observability client 7. ampli fi ed hallucinations 6½.
139. https://hollycummins.com/quarkus-ridiculous-things-voxxed-amsterdam/
140. bonus: hallucinations
141. the value of a second opinion? chatgpt.com
142. the value of a second opinion? chatgpt.com the statement we’re validating
143. the value of a second opinion? chatgpt.com the statement we’re validating “oh yes, de fi nitely true”
144. the value of a second opinion? chatgpt.com the statement we’re validating “oh yes, de fi nitely true” “what answer would you give?”
145. the value of a second opinion? chatgpt.com the statement we’re validating “oh yes, de fi nitely true” “what answer would you give?” but if you knew, why did you … ?
146. gemma3 - 1 b parameters how many bs in blueberry?
147. "Okay, let’s tackle this! As of today, October 1st, 2025, there are approximately **12** “BS”s in the word “blueberry.” It’s a surprisingly common phenomenon! 😊 Do you want to explore why this happens?" gemma3 - 1 b parameters how many bs in blueberry?
148. deepseekr1- 1.5 b parameters when did brexit happen?
149. <think> Hmm, the user is asking about something related to 20-30-0-3 but brexit, probably typo or20-10- something, correction. User meant brexit or2-1- meaning Brexit. Let me confirm that. User is20- user2 is inquiring about Brexit. UK leaving EU thing. But what time period20 2020-3 might be typo for20- 20 twenty021203. 20-20 or something. Perhaps20-202201. UK left. UK left EU. UK left20 on01 Jan201202022-021201021 I think22. Wait no1. Let me212012 January22202021. So January. Yes2 user might be21 probably20 asking about that. User22. Better2 just confirm. Brexit201 20 answer. Say20 simply22 date2. Not much else0 else0. Keep2 simple1 short1 friendly2. Okay2 polite2 user. </think> It seems you're asking about the date the Brexit, right? The UK left EU on 29th January21st of February2020221 deepseekr1- 1.5 b parameters when did brexit happen?