[{"data":1,"prerenderedAt":583},["ShallowReactive",2],{"i-lucide:chevron-down":3,"i-lucide:search":8,"i-lucide:sun":10,"i-lucide:moon":12,"i-lucide:arrow-right":14,"i-lucide:menu":16,"i-lucide:panel-left":18,"i-lucide:mail":20,"i-simple-icons:x":22,"i-simple-icons:linkedin":24,"i-simple-icons:dribbble":27,"i-simple-icons:github":29,"sidebar-course-\u002Flearn\u002Fen\u002Fcourses\u002Fcaching":31,"learn-topic-\u002Flearn\u002Fen\u002Fcourses\u002Fcaching":70,"prereq-":82,"sidebar-quiz-\u002Flearn\u002Fen\u002Fcourses\u002Fcaching":83,"lessons-\u002Flearn\u002Fen\u002Fcourses\u002Fcaching":84,"i-lucide:layers":555,"i-lucide:lock":557,"i-lucide:printer":559,"i-lucide:graduation-cap":561,"i-lucide:book-marked":563,"i-lucide:notebook-pen":565,"learn-quiz-\u002Flearn\u002Fen\u002Fcourses\u002Fcaching":83,"i-lucide:chevron-right":567,"i-lucide:workflow":569,"i-lucide:clock":571,"i-lucide:calendar":573,"i-lucide:link":575,"i-lucide:scroll-text":577,"i-lucide:book-open":579,"i-lucide:shopping-bag":581},{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":7},0,24,false,"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"m6 9l6 6l6-6\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":9},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"m21 21l-4.34-4.34\"\u002F>\u003Ccircle cx=\"11\" cy=\"11\" r=\"8\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":11},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Ccircle cx=\"12\" cy=\"12\" r=\"4\"\u002F>\u003Cpath d=\"M12 2v2m0 16v2M4.93 4.93l1.41 1.41m11.32 11.32l1.41 1.41M2 12h2m16 0h2M6.34 17.66l-1.41 1.41M19.07 4.93l-1.41 1.41\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":13},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"M20.985 12.486a9 9 0 1 1-9.473-9.472c.405-.022.617.46.402.803a6 6 0 0 0 8.268 8.268c.344-.215.825-.004.803.401\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":15},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"M5 12h14m-7-7l7 7l-7 7\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":17},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"M4 5h16M4 12h16M4 19h16\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":19},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Crect width=\"18\" height=\"18\" x=\"3\" y=\"3\" rx=\"2\"\u002F>\u003Cpath d=\"M9 3v18\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":21},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"m22 7l-8.991 5.727a2 2 0 0 1-2.009 0L2 7\"\u002F>\u003Crect width=\"20\" height=\"16\" x=\"2\" y=\"4\" rx=\"2\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":23},"\u003Cpath fill=\"currentColor\" d=\"M14.234 10.162L22.977 0h-2.072l-7.591 8.824L7.251 0H.258l9.168 13.343L.258 24H2.33l8.016-9.318L16.749 24h6.993zm-2.837 3.299l-.929-1.329L3.076 1.56h3.182l5.965 8.532l.929 1.329l7.754 11.09h-3.182z\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":25,"hidden":26},"\u003Cpath fill=\"currentColor\" d=\"M20.447 20.452h-3.554v-5.569c0-1.328-.027-3.037-1.852-3.037c-1.853 0-2.136 1.445-2.136 2.939v5.667H9.351V9h3.414v1.561h.046c.477-.9 1.637-1.85 3.37-1.85c3.601 0 4.267 2.37 4.267 5.455v6.286zM5.337 7.433a2.06 2.06 0 0 1-2.063-2.065a2.064 2.064 0 1 1 2.063 2.065m1.782 13.019H3.555V9h3.564zM22.225 0H1.771C.792 0 0 .774 0 1.729v20.542C0 23.227.792 24 1.771 24h20.451C23.2 24 24 23.227 24 22.271V1.729C24 .774 23.2 0 22.222 0z\"\u002F>",true,{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":28},"\u003Cpath fill=\"currentColor\" d=\"M12 24C5.385 24 0 18.615 0 12S5.385 0 12 0s12 5.385 12 12s-5.385 12-12 12m10.12-10.358c-.35-.11-3.17-.953-6.384-.438c1.34 3.684 1.887 6.684 1.992 7.308a10.28 10.28 0 0 0 4.395-6.87zm-6.115 7.808c-.153-.9-.75-4.032-2.19-7.77l-.066.02c-5.79 2.015-7.86 6.025-8.04 6.4a10.16 10.16 0 0 0 6.29 2.166c1.42 0 2.77-.29 4-.814zm-11.62-2.58c.232-.4 3.045-5.055 8.332-6.765q.202-.067.405-.12q-.392-.879-.832-1.74C7.17 11.775 2.206 11.71 1.756 11.7l-.004.312c0 2.633.998 5.037 2.634 6.855zm-2.42-8.955c.46.008 4.683.026 9.477-1.248a66 66 0 0 0-3.8-5.928a10.28 10.28 0 0 0-5.676 7.17zM9.6 2.052c.282.38 2.145 2.914 3.822 6c3.645-1.365 5.19-3.44 5.373-3.702A10.2 10.2 0 0 0 12 1.764c-.825 0-1.63.1-2.4.285zm10.335 3.483c-.218.29-1.935 2.493-5.724 4.04c.24.49.47.985.68 1.486c.08.18.15.36.22.53c3.41-.43 6.8.26 7.14.33c-.02-2.42-.88-4.64-2.31-6.38z\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":30},"\u003Cpath fill=\"currentColor\" d=\"M12 .297c-6.63 0-12 5.373-12 12c0 5.303 3.438 9.8 8.205 11.385c.6.113.82-.258.82-.577c0-.285-.01-1.04-.015-2.04c-3.338.724-4.042-1.61-4.042-1.61C4.422 18.07 3.633 17.7 3.633 17.7c-1.087-.744.084-.729.084-.729c1.205.084 1.838 1.236 1.838 1.236c1.07 1.835 2.809 1.305 3.495.998c.108-.776.417-1.305.76-1.605c-2.665-.3-5.466-1.332-5.466-5.93c0-1.31.465-2.38 1.235-3.22c-.135-.303-.54-1.523.105-3.176c0 0 1.005-.322 3.3 1.23c.96-.267 1.98-.399 3-.405c1.02.006 2.04.138 3 .405c2.28-1.552 3.285-1.23 3.285-1.23c.645 1.653.24 2.873.12 3.176c.765.84 1.23 1.91 1.23 3.22c0 4.61-2.805 5.625-5.475 5.92c.42.36.81 1.096.81 2.22c0 1.606-.015 2.896-.015 3.286c0 .315.21.69.825.57C20.565 22.092 24 17.592 24 12.297c0-6.627-5.373-12-12-12\"\u002F>",{"id":32,"title":33,"access":34,"body":35,"description":42,"draft":6,"estimatedMinutes":43,"extension":44,"featured":6,"icon":45,"lang":46,"level":47,"meta":48,"navigation":26,"order":49,"path":50,"prerequisites":51,"resources":52,"seo":58,"sku":56,"stem":59,"subjects":60,"summary":62,"tags":63,"updated":68,"__hash__":69},"courses\u002Flearn\u002Fen\u002Fcourses\u002Fcaching\u002Findex.md","Caching strategies","premium",{"type":36,"value":37,"toc":38},"minimark",[],{"title":39,"searchDepth":40,"depth":40,"links":41},"",3,[],"Read-through, write-behind, invalidation and the failure modes each one buys.",40,"md","lucide:layers","en","advanced",{},1,"\u002Flearn\u002Fen\u002Fcourses\u002Fcaching",[],[53],{"label":54,"file":55,"access":34,"sku":56,"size":57},"Caching decision matrix","caching-decision-matrix.pdf","topic-caching-strategies","310 KB",{"title":33,"description":42},"learn\u002Fen\u002Fcourses\u002Fcaching\u002Findex",[61],"system-design","A cache is a bet that reading stale data is cheaper than reading correct data.\nThe strategies differ in who writes to the cache, when, and what happens when\nthe cache and the source disagree. Cache-aside is the default because it fails\nsafely. Write-behind is the fastest and loses data on a crash. Almost every\nproduction incident involving a cache comes down to invalidation, stampedes, or\na cache that was quietly doing nothing at all.\n",[64,65,66,67],"caching","performance","consistency","redis","2026-08-06","mqYWifp5mzccLyzSY681N-Yn1wymognvHpRRfhOtFBI",{"id":32,"title":33,"access":34,"body":71,"description":42,"draft":6,"estimatedMinutes":43,"extension":44,"featured":6,"icon":45,"lang":46,"level":47,"meta":75,"navigation":26,"order":49,"path":50,"prerequisites":76,"resources":77,"seo":79,"sku":56,"stem":59,"subjects":80,"summary":62,"tags":81,"updated":68,"__hash__":69},{"type":36,"value":72,"toc":73},[],{"title":39,"searchDepth":40,"depth":40,"links":74},[],{},[],[78],{"label":54,"file":55,"access":34,"sku":56,"size":57},{"title":33,"description":42},[61],[64,65,66,67],[],null,[85,314],{"id":86,"title":87,"access":88,"body":89,"description":308,"extension":44,"lang":46,"meta":309,"navigation":26,"order":49,"partial":26,"path":310,"seo":311,"stem":312,"__hash__":313},"lessons\u002Flearn\u002Fen\u002Fcourses\u002Fcaching\u002F01.strategies.md","The four strategies","free",{"type":36,"value":90,"toc":302},[91,95,99,104,107,259,262,266,269,272,276,279,282,286,289,292,298],[92,93,87],"h1",{"id":94},"the-four-strategies",[96,97,98],"p",{},"Every caching pattern answers two questions: who populates the cache, and when is\nthe source of truth updated relative to it.",[100,101,103],"h2",{"id":102},"cache-aside","Cache-aside",[96,105,106],{},"The application checks the cache, and on a miss reads the database and populates\nthe cache itself. The cache has no knowledge of the database.",[108,109,113],"pre",{"className":110,"code":111,"language":112,"meta":39,"style":39},"language-python shiki shiki-themes github-dark-dimmed github-dark-dimmed","def get_user(user_id):\n    cached = cache.get(f\"user:{user_id}\")\n    if cached is not None:\n        return cached\n    user = db.query(\"SELECT * FROM users WHERE id = %s\", user_id)\n    cache.set(f\"user:{user_id}\", user, ttl=300)\n    return user\n","python",[114,115,116,132,166,187,196,218,250],"code",{"__ignoreMap":39},[117,118,120,124,128],"span",{"class":119,"line":49},"line",[117,121,123],{"class":122},"sEYkB","def",[117,125,127],{"class":126},"s-wk_"," get_user",[117,129,131],{"class":130},"sM9_K","(user_id):\n",[117,133,135,138,141,144,147,151,154,157,160,163],{"class":119,"line":134},2,[117,136,137],{"class":130},"    cached ",[117,139,140],{"class":122},"=",[117,142,143],{"class":130}," cache.get(",[117,145,146],{"class":122},"f",[117,148,150],{"class":149},"szYpP","\"user:",[117,152,153],{"class":122},"{",[117,155,156],{"class":130},"user_id",[117,158,159],{"class":122},"}",[117,161,162],{"class":149},"\"",[117,164,165],{"class":130},")\n",[117,167,168,171,174,177,180,184],{"class":119,"line":40},[117,169,170],{"class":122},"    if",[117,172,173],{"class":130}," cached ",[117,175,176],{"class":122},"is",[117,178,179],{"class":122}," not",[117,181,183],{"class":182},"sQdni"," None",[117,185,186],{"class":130},":\n",[117,188,190,193],{"class":119,"line":189},4,[117,191,192],{"class":122},"        return",[117,194,195],{"class":130}," cached\n",[117,197,199,202,204,207,210,213,215],{"class":119,"line":198},5,[117,200,201],{"class":130},"    user ",[117,203,140],{"class":122},[117,205,206],{"class":130}," db.query(",[117,208,209],{"class":149},"\"SELECT * FROM users WHERE id = ",[117,211,212],{"class":122},"%s",[117,214,162],{"class":149},[117,216,217],{"class":130},", user_id)\n",[117,219,221,224,226,228,230,232,234,236,239,243,245,248],{"class":119,"line":220},6,[117,222,223],{"class":130},"    cache.set(",[117,225,146],{"class":122},[117,227,150],{"class":149},[117,229,153],{"class":122},[117,231,156],{"class":130},[117,233,159],{"class":122},[117,235,162],{"class":149},[117,237,238],{"class":130},", user, ",[117,240,242],{"class":241},"siJwO","ttl",[117,244,140],{"class":122},[117,246,247],{"class":182},"300",[117,249,165],{"class":130},[117,251,253,256],{"class":119,"line":252},7,[117,254,255],{"class":122},"    return",[117,257,258],{"class":130}," user\n",[96,260,261],{},"This is the default for a reason: if the cache is down, every request simply\nbecomes a database read. Degraded, not broken.",[100,263,265],{"id":264},"read-through","Read-through",[96,267,268],{},"The cache sits inline. The application only talks to the cache, which fetches from\nthe database on a miss. Logic moves out of the application and into the cache layer.",[96,270,271],{},"Cleaner call sites, but the cache is now on the critical path — if it is unavailable,\nreads fail entirely rather than falling back.",[100,273,275],{"id":274},"write-through","Write-through",[96,277,278],{},"Writes go to the cache, which synchronously writes to the database before\nacknowledging. The cache is never stale.",[96,280,281],{},"The cost is write latency: every write pays for both hops. Worth it when reads\nvastly outnumber writes and stale reads are unacceptable.",[100,283,285],{"id":284},"write-behind","Write-behind",[96,287,288],{},"Writes land in the cache and are flushed to the database asynchronously.",[96,290,291],{},"Fastest writes available, and the only strategy that can lose acknowledged data. A\ncrash between acknowledgement and flush loses whatever was buffered.",[293,294,295],"warning",{},[96,296,297],{},"Write-behind is appropriate for metrics, view counts and analytics events. It is not\nappropriate for anything a user would notice going missing — orders, payments,\nmessages. The performance gain is real, and so is the data loss.",[299,300,301],"style",{},"html pre.shiki code .sEYkB, html code.shiki .sEYkB{--shiki-default:#F47067;--shiki-dark:#F47067}html pre.shiki code .s-wk_, html code.shiki .s-wk_{--shiki-default:#DCBDFB;--shiki-dark:#DCBDFB}html pre.shiki code .sM9_K, html code.shiki .sM9_K{--shiki-default:#ADBAC7;--shiki-dark:#ADBAC7}html pre.shiki code .szYpP, html code.shiki .szYpP{--shiki-default:#96D0FF;--shiki-dark:#96D0FF}html pre.shiki code .sQdni, html code.shiki .sQdni{--shiki-default:#6CB6FF;--shiki-dark:#6CB6FF}html pre.shiki code .siJwO, html code.shiki .siJwO{--shiki-default:#F69D50;--shiki-dark:#F69D50}html .default .shiki span {color: var(--shiki-default);background: var(--shiki-default-bg);font-style: var(--shiki-default-font-style);font-weight: var(--shiki-default-font-weight);text-decoration: var(--shiki-default-text-decoration);}html .shiki span {color: var(--shiki-default);background: var(--shiki-default-bg);font-style: var(--shiki-default-font-style);font-weight: var(--shiki-default-font-weight);text-decoration: var(--shiki-default-text-decoration);}html .dark .shiki span {color: var(--shiki-dark);background: var(--shiki-dark-bg);font-style: var(--shiki-dark-font-style);font-weight: var(--shiki-dark-font-weight);text-decoration: var(--shiki-dark-text-decoration);}html.dark .shiki span {color: var(--shiki-dark);background: var(--shiki-dark-bg);font-style: var(--shiki-dark-font-style);font-weight: var(--shiki-dark-font-weight);text-decoration: var(--shiki-dark-text-decoration);}",{"title":39,"searchDepth":40,"depth":40,"links":303},[304,305,306,307],{"id":102,"depth":134,"text":103},{"id":264,"depth":134,"text":265},{"id":274,"depth":134,"text":275},{"id":284,"depth":134,"text":285},"Cache-aside, read-through, write-through and write-behind compared.",{},"\u002Flearn\u002Fen\u002Fcourses\u002Fcaching\u002Fstrategies",{"title":87,"description":308},"learn\u002Fen\u002Fcourses\u002Fcaching\u002F01.strategies","sh2NUIv6r7JjhJWD_OzLrfaRSj7urg2L7nJtqWFgm04",{"id":315,"title":316,"access":34,"body":317,"description":549,"extension":44,"lang":46,"meta":550,"navigation":26,"order":134,"partial":6,"path":551,"seo":552,"stem":553,"__hash__":554},"lessons\u002Flearn\u002Fen\u002Fcourses\u002Fcaching\u002F02.invalidation.md","Invalidation and stampedes",{"type":36,"value":318,"toc":543},[319,322,325,329,332,336,339,342,345,352,358,427,433,439,443,446,485,488,491,495,498,537,540],[92,320,316],{"id":321},"invalidation-and-stampedes",[96,323,324],{},"Caching is easy. Knowing when the cached value stopped being true is the hard part.",[100,326,328],{"id":327},"ttl-is-a-guess-about-staleness","TTL is a guess about staleness",[96,330,331],{},"A TTL says \"I accept being wrong for up to this long\". Choosing one means deciding\nhow much staleness the product tolerates — a question for the product, not the\ninfrastructure.",[100,333,335],{"id":334},"the-thundering-herd","The thundering herd",[96,337,338],{},"A popular key expires. A thousand concurrent requests miss simultaneously. All\nthousand hit the database with the same query.",[96,340,341],{},"The database, sized for the cached load, falls over. Recovery repopulates the cache,\nthe key expires again, and the pattern repeats on a cycle matching the TTL.",[96,343,344],{},"Three defences:",[96,346,347,351],{},[348,349,350],"strong",{},"Locking."," The first miss takes a lock and recomputes; everyone else waits or\nserves stale. Correct, but adds a coordination point.",[96,353,354,357],{},[348,355,356],{},"Probabilistic early expiry."," Recompute before expiry with a probability that\nrises as the TTL approaches, so refreshes spread out instead of synchronising.",[108,359,361],{"className":110,"code":360,"language":112,"meta":39,"style":39},"def should_refresh(computed_at, ttl, beta=1.0):\n    age = now() - computed_at\n    return age + beta * delta * math.log(random.random()) >= ttl\n",[114,362,363,381,397],{"__ignoreMap":39},[117,364,365,367,370,373,375,378],{"class":119,"line":49},[117,366,123],{"class":122},[117,368,369],{"class":126}," should_refresh",[117,371,372],{"class":130},"(computed_at, ttl, beta",[117,374,140],{"class":122},[117,376,377],{"class":182},"1.0",[117,379,380],{"class":130},"):\n",[117,382,383,386,388,391,394],{"class":119,"line":134},[117,384,385],{"class":130},"    age ",[117,387,140],{"class":122},[117,389,390],{"class":130}," now() ",[117,392,393],{"class":122},"-",[117,395,396],{"class":130}," computed_at\n",[117,398,399,401,404,407,410,413,416,418,421,424],{"class":119,"line":40},[117,400,255],{"class":122},[117,402,403],{"class":130}," age ",[117,405,406],{"class":122},"+",[117,408,409],{"class":130}," beta ",[117,411,412],{"class":122},"*",[117,414,415],{"class":130}," delta ",[117,417,412],{"class":122},[117,419,420],{"class":130}," math.log(random.random()) ",[117,422,423],{"class":122},">=",[117,425,426],{"class":130}," ttl\n",[96,428,429,432],{},[348,430,431],{},"Jitter."," Add randomness to every TTL so keys written together do not expire\ntogether. The cheapest fix and often sufficient.",[434,435,436],"danger",{},[96,437,438],{},"Populating a cache during a deploy or a warm-up script writes thousands of keys\nwithin the same second. With a fixed TTL they all expire within the same second too,\nproducing a synchronised stampede hours later that looks completely unrelated to\nthe deploy that caused it. Always jitter.",[100,440,442],{"id":441},"explicit-invalidation","Explicit invalidation",[96,444,445],{},"Delete the key on write:",[108,447,449],{"className":110,"code":448,"language":112,"meta":39,"style":39},"def update_user(user_id, data):\n    db.update(user_id, data)\n    cache.delete(f\"user:{user_id}\")\n",[114,450,451,461,466],{"__ignoreMap":39},[117,452,453,455,458],{"class":119,"line":49},[117,454,123],{"class":122},[117,456,457],{"class":126}," update_user",[117,459,460],{"class":130},"(user_id, data):\n",[117,462,463],{"class":119,"line":134},[117,464,465],{"class":130},"    db.update(user_id, data)\n",[117,467,468,471,473,475,477,479,481,483],{"class":119,"line":40},[117,469,470],{"class":130},"    cache.delete(",[117,472,146],{"class":122},[117,474,150],{"class":149},[117,476,153],{"class":122},[117,478,156],{"class":130},[117,480,159],{"class":122},[117,482,162],{"class":149},[117,484,165],{"class":130},[96,486,487],{},"Delete rather than overwrite. Overwriting introduces a race where two concurrent\nwriters leave the cache holding the older value.",[96,489,490],{},"The ordering matters too — database first, then cache. Reversed, a concurrent read\nbetween the two steps repopulates the cache with the old row and the stale value\nsurvives its TTL.",[100,492,494],{"id":493},"cached-nothing","Cached nothing",[96,496,497],{},"The failure mode nobody instruments: a cache that works perfectly and is never hit,\nbecause keys are built from something that varies per request.",[108,499,501],{"className":110,"code":500,"language":112,"meta":39,"style":39},"cache.set(f\"user:{user_id}:{request_id}\", user)  # unique every time\n",[114,502,503],{"__ignoreMap":39},[117,504,505,508,510,512,514,516,518,521,523,526,528,530,533],{"class":119,"line":49},[117,506,507],{"class":130},"cache.set(",[117,509,146],{"class":122},[117,511,150],{"class":149},[117,513,153],{"class":122},[117,515,156],{"class":130},[117,517,159],{"class":122},[117,519,520],{"class":149},":",[117,522,153],{"class":122},[117,524,525],{"class":130},"request_id",[117,527,159],{"class":122},[117,529,162],{"class":149},[117,531,532],{"class":130},", user)  ",[117,534,536],{"class":535},"s0RzX","# unique every time\n",[96,538,539],{},"Hit rate is zero. Latency is unchanged. Nothing errors. Monitor hit rate as a first\nclass metric, and alert when it drops — a cache silently doing nothing is a cost with\nno benefit.",[299,541,542],{},"html pre.shiki code .sEYkB, html code.shiki .sEYkB{--shiki-default:#F47067;--shiki-dark:#F47067}html pre.shiki code .s-wk_, html code.shiki .s-wk_{--shiki-default:#DCBDFB;--shiki-dark:#DCBDFB}html pre.shiki code .sM9_K, html code.shiki .sM9_K{--shiki-default:#ADBAC7;--shiki-dark:#ADBAC7}html pre.shiki code .sQdni, html code.shiki .sQdni{--shiki-default:#6CB6FF;--shiki-dark:#6CB6FF}html .default .shiki span {color: var(--shiki-default);background: var(--shiki-default-bg);font-style: var(--shiki-default-font-style);font-weight: var(--shiki-default-font-weight);text-decoration: var(--shiki-default-text-decoration);}html .shiki span {color: var(--shiki-default);background: var(--shiki-default-bg);font-style: var(--shiki-default-font-style);font-weight: var(--shiki-default-font-weight);text-decoration: var(--shiki-default-text-decoration);}html .dark .shiki span {color: var(--shiki-dark);background: var(--shiki-dark-bg);font-style: var(--shiki-dark-font-style);font-weight: var(--shiki-dark-font-weight);text-decoration: var(--shiki-dark-text-decoration);}html.dark .shiki span {color: var(--shiki-dark);background: var(--shiki-dark-bg);font-style: var(--shiki-dark-font-style);font-weight: var(--shiki-dark-font-weight);text-decoration: var(--shiki-dark-text-decoration);}html pre.shiki code .szYpP, html code.shiki .szYpP{--shiki-default:#96D0FF;--shiki-dark:#96D0FF}html pre.shiki code .s0RzX, html code.shiki .s0RzX{--shiki-default:#768390;--shiki-dark:#768390}",{"title":39,"searchDepth":40,"depth":40,"links":544},[545,546,547,548],{"id":327,"depth":134,"text":328},{"id":334,"depth":134,"text":335},{"id":441,"depth":134,"text":442},{"id":493,"depth":134,"text":494},"TTLs, explicit invalidation, and what happens when a hot key expires.",{},"\u002Flearn\u002Fen\u002Fcourses\u002Fcaching\u002Finvalidation",{"title":316,"description":549},"learn\u002Fen\u002Fcourses\u002Fcaching\u002F02.invalidation","fahMLdo2hiDD5K_BQHGZCeYMOkIquLGdRIDAy0WkguI",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":556},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M12.83 2.18a2 2 0 0 0-1.66 0L2.6 6.08a1 1 0 0 0 0 1.83l8.58 3.91a2 2 0 0 0 1.66 0l8.58-3.9a1 1 0 0 0 0-1.83z\"\u002F>\u003Cpath d=\"M2 12a1 1 0 0 0 .58.91l8.6 3.91a2 2 0 0 0 1.65 0l8.58-3.9A1 1 0 0 0 22 12\"\u002F>\u003Cpath d=\"M2 17a1 1 0 0 0 .58.91l8.6 3.91a2 2 0 0 0 1.65 0l8.58-3.9A1 1 0 0 0 22 17\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":558},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Crect width=\"18\" height=\"11\" x=\"3\" y=\"11\" rx=\"2\" ry=\"2\"\u002F>\u003Cpath d=\"M7 11V7a5 5 0 0 1 10 0v4\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":560},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M6 18H4a2 2 0 0 1-2-2v-5a2 2 0 0 1 2-2h16a2 2 0 0 1 2 2v5a2 2 0 0 1-2 2h-2M6 9V3a1 1 0 0 1 1-1h10a1 1 0 0 1 1 1v6\"\u002F>\u003Crect width=\"12\" height=\"8\" x=\"6\" y=\"14\" rx=\"1\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":562},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M21.42 10.922a1 1 0 0 0-.019-1.838L12.83 5.18a2 2 0 0 0-1.66 0L2.6 9.08a1 1 0 0 0 0 1.832l8.57 3.908a2 2 0 0 0 1.66 0zM22 10v6\"\u002F>\u003Cpath d=\"M6 12.5V16a6 3 0 0 0 12 0v-3.5\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":564},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M10 2v8l3-3l3 3V2\"\u002F>\u003Cpath d=\"M4 19.5v-15A2.5 2.5 0 0 1 6.5 2H19a1 1 0 0 1 1 1v18a1 1 0 0 1-1 1H6.5a1 1 0 0 1 0-5H20\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":566},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M13.4 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2v-7.4M2 6h4m-4 4h4m-4 4h4m-4 4h4\"\u002F>\u003Cpath d=\"M21.378 5.626a1 1 0 1 0-3.004-3.004l-5.01 5.012a2 2 0 0 0-.506.854l-.837 2.87a.5.5 0 0 0 .62.62l2.87-.837a2 2 0 0 0 .854-.506z\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":568},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"m9 18l6-6l-6-6\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":570},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Crect width=\"8\" height=\"8\" x=\"3\" y=\"3\" rx=\"2\"\u002F>\u003Cpath d=\"M7 11v4a2 2 0 0 0 2 2h4\"\u002F>\u003Crect width=\"8\" height=\"8\" x=\"13\" y=\"13\" rx=\"2\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":572},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Ccircle cx=\"12\" cy=\"12\" r=\"10\"\u002F>\u003Cpath d=\"M12 6v6l4 2\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":574},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M8 2v3m8-3v3\"\u002F>\u003Crect width=\"18\" height=\"18\" x=\"3\" y=\"3\" rx=\"2\"\u002F>\u003Cpath d=\"M3 9h18\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":576},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71\"\u002F>\u003Cpath d=\"M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":578},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M15 12h-5m5-4h-5m9 9V5a2 2 0 0 0-2-2H4\"\u002F>\u003Cpath d=\"M8 21h12a2 2 0 0 0 2-2v-1a1 1 0 0 0-1-1H11a1 1 0 0 0-1 1v1a2 2 0 1 1-4 0V5a2 2 0 1 0-4 0v2a1 1 0 0 0 1 1h3\"\u002F>\u003C\u002Fg>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":580},"\u003Cpath fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\" d=\"M12 5v16m8.001-2A2 2 0 0 0 22 17V5a2 2 0 0 0-1.999-2L16 3.002A5 5 0 0 0 12 5a5 5 0 0 0-4-2H4a2 2 0 0 0-2 2v12a2 2 0 0 0 1.999 2H8a5 5 0 0 1 4 2a5 5 0 0 1 4-2z\"\u002F>",{"left":4,"top":4,"width":5,"height":5,"rotate":4,"vFlip":6,"hFlip":6,"body":582},"\u003Cg fill=\"none\" stroke=\"currentColor\" stroke-linecap=\"round\" stroke-linejoin=\"round\" stroke-width=\"2\">\u003Cpath d=\"M16 10a4 4 0 0 1-8 0M3.103 6.034h17.794\"\u002F>\u003Cpath d=\"M3.4 5.467a2 2 0 0 0-.4 1.2V20a2 2 0 0 0 2 2h14a2 2 0 0 0 2-2V6.667a2 2 0 0 0-.4-1.2l-2-2.667A2 2 0 0 0 17 2H7a2 2 0 0 0-1.6.8z\"\u002F>\u003C\u002Fg>",1787597894629]