In addition to choosing between SQL or NoSQL, it is helpful to understand which type of NoSQL database best fits your use case(s). Federation is not effective if your schema requires huge functions or tables. For example, instead of a single, monolithic database, you could have three databases: forums, users, and products, resulting in less read and write traffic to each database and therefore less replication lag. Users are generally more tolerant of latency when updating data than reading data. Each service runs a unique process and communicates through a well-defined, lightweight mechanism to serve a business goal. Next, we'll look at high-level trade-offs: Keep in mind that everything is a trade-off. 7 1288 25610 1024 1 thousand 1 KB16 65,536 64 KB20 1,048,576 1 million 1 MB30 1,073,741,824 1 billion 1 GB32 4,294,967,296 4 GB40 1,099,511,627,776 1 trillion 1 TB```, L1 cache reference 0.5 nsBranch mispredict 5 nsL2 cache reference 7 ns 14x L1 cacheMutex lock/unlock 25 nsMain memory reference 100 ns 20x L2 cache, 200x L1 cacheCompress 1K bytes with Zippy 10,000 ns 10 usSend 1 KB bytes over 1 Gbps network 10,000 ns 10 usRead 4 KB randomly from SSD* 150,000 ns 150 us ~1GB/sec SSDRead 1 MB sequentially from memory 250,000 ns 250 usRound trip within same datacenter 500,000 ns 500 usRead 1 MB sequentially from SSD* 1,000,000 ns 1,000 us 1 ms ~1GB/sec SSD, 4X memoryHDD seek 10,000,000 ns 10,000 us 10 ms 20x datacenter roundtripRead 1 MB sequentially from 1 Gbps 10,000,000 ns 10,000 us 10 ms 40x memory, 10X SSDRead 1 MB sequentially from HDD 30,000,000 ns 30,000 us 30 ms 120x memory, 30X SSDSend packet CA->Netherlands->CA 150,000,000 ns 150,000 us 150 ms, 1 ns = 10^-9 seconds1 us = 10^-6 seconds = 1,000 ns1 ms = 10^-3 seconds = 1,000 us = 1,000,000 ns```. Dropbox System Design. For internal communications, we could use Remote Procedure Calls. Your router or ISP provides information about which DNS server(s) to contact when doing a lookup. CP is a good choice if your business needs require atomic reads and writes. You want to control how error control happens off your library. If the master goes offline, the system can continue to operate in read-only mode until a slave is promoted to a master or a new master is provisioned. Once the queue fills up, clients get a server busy or HTTP 503 status code to try again later. We could use a relational database as a large hash table, mapping the generated url to a file server and path containing the paste file. Thus, proper primer designis necessary for successful DNA amplification. The single responsibility principle advocates for small and autonomous services that work together. Tasks queues receive tasks and their related data, runs them, then delivers their results. Learn how to design large-scale systems. Otherwise, we'll need to employ additional SQL scaling patterns: We should also consider moving some data to a NoSQL Database. Learning how to design scalable systems will help you become a better engineer. Datagrams might reach their destination out of order or not at all. REST typically relies on a few verbs (GET, POST, PUT, DELETE, and PATCH) which sometimes doesn't fit your use case. The application is responsible for reading and writing from storage. RPC is focused on exposing behaviors. Each value contains a timestamp for versioning and for conflict resolution. UDP does not support congestion control. High level observations: 1. Business level constraints (time, human, fiscal and other resources, stakeholders) trump technical constraints every time. Primer Design for PCR. Don't focus on nitty gritty details for the following articles, instead: |Type | System | Reference(s) ||---|---|---|| Data processing | MapReduce - Distributed data processing from Google | || Data processing | Spark - Distributed data processing from Databricks | || Data processing | Storm - Distributed data processing from Twitter | || | | || Data store | Bigtable - Distributed column-oriented database from Google | || Data store | HBase - Open source implementation of Bigtable | || Data store | Cassandra - Distributed column-oriented database from Facebook || Data store | DynamoDB - Document-oriented database from Amazon | || Data store | MongoDB - Document-oriented database | || Data store | Spanner - Globally-distributed database from Google | || Data store | Memcached - Distributed memory caching system | || Data store | Redis - Distributed memory caching system with persistence and value types | || | | || File system | Google File System (GFS) - Distributed file system | || File system | Hadoop File System (HDFS) - Open source implementation of GFS | || | | || Misc | Chubby - Lock service for loosely-coupled distributed systems from Google | || Misc | Dapper - Distributed systems tracing infrastructure || Misc | Kafka - Pub/sub message queue from LinkedIn | || Misc | Zookeeper - Centralized infrastructure and services enabling synchronization | || | Add an architecture | Contribute |, | Company | Reference(s) ||---|---|| Amazon | Amazon architecture || Cinchcast | Producing 1,500 hours of audio every day || DataSift | Realtime datamining At 120,000 tweets per second || DropBox | How we've scaled Dropbox || ESPN | Operating At 100,000 duh nuh nuhs per second || Google | Google architecture || Instagram | 14 million users, terabytes of photosWhat powers Instagram || | Justin.Tv's live video broadcasting architecture || Facebook | Scaling memcached at FacebookTAO: Facebook’s distributed data store for the social graphFacebook’s photo storageHow Facebook Live Streams To 800,000 Simultaneous Viewers || Flickr | Flickr architecture || Mailbox | From 0 to one million users in 6 weeks || Netflix | A 360 Degree View Of The Entire Netflix StackNetflix: What Happens When You Press Play? Accessing a DNS server introduces a slight delay, although mitigated by caching described above. This issue is mitigated by setting a time-to-live (TTL) which forces an update of the cache entry, or by using write-through. 4 average paste writes per second (with higher at peak) should be do-able for a single SQL Write Master-Slave. BASE is often used to describe the properties of NoSQL databases. fetching content of a blog entry and the comments on that entry. Most NoSQL stores lack true ACID transactions and favor eventual consistency. For example, moving expired documents to the archive folder might not cleanly fit within these verbs. Netflix: What Happens When You Press Play? Strong consistency works well in systems that need transactions. We'll review key-value stores, document stores, wide column stores, and graph databases in the next section. Source: Crack the system design interview. It is more complex to implement write-behind than it is to implement cache-aside or write-through. A new API must be defined for every new operation or use case. Data is replicated synchronously. You can use the following steps to guide the discussion. Layer 7 load balancers look at the application layer to decide how to distribute requests. Top tech companies are likely to have one or more design interview rounds. It minimizes the coupling between client/server and is often used for public HTTP APIs. DNS server management could be complex and is generally managed by, Users receive content from data centers close to them, Your servers do not have to serve requests that the CDN fulfills. If there are a lot of writes, the read replicas can get bogged down with replaying writes and can't do as many reads. Design Systems by Alla Kholmatova - pretty much the canonical design systems book; Expressive Design Systems by Yesenia Perez-Cruz - a great follow-up to Kholmatova's book; Atomic Design by Brad Frost - written before we were using the term 'design system' for web interfaces, but many of the popular ideas extend from … A Domain Name System (DNS) translates a domain name such as to an IP address. Prevent traffic from going to servers under maintenance. With no single central master serializing writes you can write in parallel, increasing throughput. Address bottlenecks using principles of scalable system design. For efficient priming, the design tool avoids primers with extensive self-dimer and cross dimer formations in order to minimize primer secondary structure and primer dimer formation. Both Consul and Etcd have a built in key-value store that can be useful for storing config values and other shared data. Kann man auch nur Primer benutzen? HTTP is self-contained, allowing requests and responses to flow through many intermediate routers and servers that perform load balancing, caching, encryption, and compression. Start broad and go deeper in a few areas. Google introduced Bigtable as the first wide column store, which influenced the open-source HBase often-used in the Hadoop ecosystem, and Cassandra from Facebook. Then we'll dive into more specific topics such as DNS, CDNs, and load balancers. This video covers what is CAP theorem along with the trade offs in choosing a database with real world examples. Graph databases are optimized to represent complex relationships with many foreign keys or many-to-many relationships. Key differences between TCP and UDP protocols, Do you really know why you prefer REST over RPC. Ask questions to clarify use cases and constraints. Instead of managing a file server, we could use a managed Object Store such as Amazon S3 or a NoSQL document store. Benchmarking and profiling might point you to the following optimizations. For example, you might need to determine how long it will take to generate 100 image thumbnails from disk or how much memory a data structure will take. Popular RPC frameworks include Protobuf, Thrift, and Avro. Health checks help verify service integrity and are often done using an HTTP endpoint. Although documents can be organized or grouped together, documents may have fields that are completely different from each other. Workers in the application layer also help enable asynchronism. In general, a length of 18–30 nucleotides for primers is good. In active-active, both servers are managing traffic, spreading the load between them. system-design-primer / solutions / system_design / pastebin / Go to file Go to file T; Go to line L; Copy path John-Richardson Remove redundant SQL index in Pastebin exercise . In this model, the dispatcher will first lookup if the request has been made before and try to find the previous result to return, in order to save the actual execution. Have your application assemble the dataset from the database into a class instance or a data structure(s): Since you can only store a limited amount of data in cache, you'll need to determine which cache update strategy works best for your use case. Joining data from two databases is more complex with a. Federation adds more hardware and additional complexity. We'll create an additional index on created_at to speed up lookups (log-time instead of scanning the entire table) and to keep the data in memory. Being stateless, REST is great for horizontal scaling and partitioning. Use parameterized queries to prevent SQL injection. Writes are replayed to the read replicas. Primer-blast tries to find target-specific primers by placing candidate primers on unique template regions that are not similar to other targets. Weak consistency works well in real time use cases such as VoIP, video chat, and realtime multiplayer games. The SQL Read Replicas should be able to handle the cache misses, as long as the replicas are not bogged down with replicating writes. System Design Primer A collection of System Design interview questions & their solutions. Generally, this involves the source, destination IP addresses, and ports in the header, but not the contents of the packet. Discuss assumptions. Without an interviewer to address clarifying questions, we'll define some use cases and constraints. Ihrer Kreativität sind keine Grenzen gesetzt. Because this is my personal repository, the license you receive to my code and resources is from me and not my employer (Facebook). Remove redundant SQL index in Pastebin exercise (, Design a system that scales to millions of users on AWS, Relational database management system (RDBMS), Latency numbers every programmer should know, Page view analytics do not need to be realtime, 1.27 KB per paste * 10 million pastes per month, Assume most are new pastes instead of updates to existing ones, 1 request per second = 2.5 million requests per month, 40 requests per second = 100 million requests per month, 400 requests per second = 1 billion requests per month, Checks if the url is unique by looking at the, If the url is not unique, it generates another url, If we supported a custom url, we could use the user-supplied (also check for a duplicate), MD5 is a widely used hashing function that produces a 128-bit hash value, Alternatively, we could also take the MD5 hash of randomly-generated data, There is only one hash result for the original input and Base 62 is deterministic (no randomness involved), Base 64 is another popular encoding but provides issues for urls because of the additional. The Memory Cache is also useful for handling the unevenly distributed traffic and traffic spikes. At the cost of flexibility, layer 4 load balancing requires less time and computing resources than Layer 7, although the performance impact can be minimal on modern commodity hardware. They can also help by doing time-consuming work in advance, such as periodic aggregation of data. Load balancers can also help with horizontal scaling, improving performance and availability. Services such as CloudFlare and Route 53 provide managed DNS services. Click on the "Design Primers" button to get a list of appropriate PCR primer pairs. | Duration | Acceptable downtime||---------------------|--------------------|| Downtime per year | 8h 45min 57s || Downtime per month | 43m 49.7s || Downtime per week | 10m 4.8s || Downtime per day | 1m 26.4s |, | Duration | Acceptable downtime||---------------------|--------------------|| Downtime per year | 52min 35.7s || Downtime per month | 4m 23s || Downtime per week | 1m 5s || Downtime per day | 8.6s |. Below are common HTTP verbs: | Verb | Description | Idempotent* | Safe | Cacheable ||---|---|---|---|---|| GET | Reads a resource | Yes | Yes | Yes || POST | Creates a resource or trigger a process that handles data | No | No | Yes if response contains freshness info || PUT | Creates or replace a resource | Yes | No | No || PATCH | Partially updates a resource | No | No | Yes if response contains freshness info || DELETE | Deletes a resource | Yes | No | No |. Datagrams (analogous to packets) are guaranteed only at the datagram level. Reverse proxies and caches such as Varnish can serve static and dynamic content directly. Clients can retry the request at a later time, perhaps with exponential backoff. All packets sent are guaranteed to reach the destination in the original order and without corruption through: If the sender does not receive a correct response, it will resend the packets. In comparison with the CAP Theorem, BASE chooses availability over consistency. TCP also implements flow control and congestion control. As machine learning becomes more and more adopted in … Redis has the following additional features: There are multiple levels you can cache that fall into two general categories: database queries and objects: Generally, you should try to avoid file-based caching, as it makes cloning and auto-scaling more difficult. After a write, reads may or may not see it. Another way to look at performance vs scalability: Latency is the time to perform some action or to produce some result. For example, if you are on a phone call and lose reception for a few seconds, when you regain connection you do not hear what was spoken during connection loss. You'll need to update your application logic to determine which database to read and write. Security is a broad topic. I am providing code and resources in this repository to you under an open source license. Requests from clients are forwarded to a server that can fulfill it before the reverse proxy returns the server's response to the client. Bases at the 5'-end of the primer are less critical for primer annealing. Therefore, it is possible to add sequence elements, like restriction sites, to the 5'-end of the primer molecule. This style guide is living documentation that will be updated as we continue to improve and evolve our design system. There is a vast amount of resources scattered throughout the web on system design principles. on December 10, 2020, There are no reviews yet. Both masters serve reads and writes and coordinate with each other on writes. Common ways to shard a table of users is either through the user's last name initial or the user's geographic location. Gather requirements and scope the problem. Data is replicated asynchronously. You'll need to make a software tradeoff between consistency and availability. An Object Store such as Amazon S3 can comfortably handle the constraint of 12.7 GB of new content per month. If the heartbeat is interrupted, the passive server takes over the active's IP address and resumes service. They can support scheduling and can be used to run computationally-intensive jobs in the background. Document stores provide high flexibility and are often used for working with occasionally changing data. This section could use some updates. Web servers can also cache requests, returning responses without having to contact application servers. Primer design tips. Sharding adds more hardware and additional complexity. The cache does not interact with storage directly. In write-behind, the application does the following: You can configure the cache to automatically refresh any recently accessed cache entry prior to its expiration. You want to control how your "logic" is accessed. Break up a table by putting hot spots in a separate table to help keep it in memory. Availability is generally measured in number of 9s--a service with 99.99% availability is described as having four 9s. Data can become stale if it is updated in the database. To protect against failures, it's common to set up multiple load balancers, either in active-passive or active-active mode. Slaves can also replicate to additional slaves in a tree-like fashion. Amazon SQS is hosted but can have high latency and has the possibility of messages being delivered twice. Architects or team leads might be expected to know more than individual contributors. For example, if you were asked to design a url shortening service, discuss: Identify and address bottlenecks, given the constraints. If the servers are public-facing, the DNS would need to know about the public IPs of both servers. When loading large amounts of data, it might be faster to disable indices, load the data, then rebuild the indices. Content might be stale if it is updated before the TTL expires it. Performance and end user experience is your primary concern. Cache invalidation is a difficult problem, there is additional complexity associated with when to update the cache. A denormalized database under heavy write load might perform worse than its normalized counterpart. Sharding distributes data across different databases such that each database can only manage a subset of the data. Primers are alwa… UDP can broadcast, sending datagrams to all devices on the subnet. Based on the underlying implementation, documents are organized by collections, tags, metadata, or directories. Need to make application changes such as adding Redis or memcached. Overall availability increases when two components with availability < 100% are in parallel: Availability (Total) = 1 - (1 - Availability (Foo)) * (1 - Availability (Bar)). | Operation | RPC | REST ||---|---|---|| Signup | POST /signup | POST /persons || Resign | POST /resign{"personid": "1234"} | DELETE /persons/1234 || Read a person | GET /readPerson?personid=1234 | GET /persons/1234 || Read a person’s items list | GET /readUsersItemsList?personid=1234 | GET /persons/1234/items || Add an item to a person’s items | POST /addItemToUsersItemsList{"personid": "1234";"itemid": "456"} | POST /persons/1234/items{"itemid": "456"} || Update an item | POST /modifyItem{"itemid": "456";"key": "value"} | PUT /items/456{"key": "value"} || Delete an item | POST /removeItem{"itemid": "456"} | DELETE /items/456 |, Source: Do you really know why you prefer REST over RPC. Clarify with your interviewer if you should run back-of-the-envelope usage calculations. Cache-aside in conjunction with write through can mitigate this issue. Sketch the main components and connections, Generating and storing a hash of the full url. Deploying a load balancer is useful when you have multiple servers. All expired entries would then be deleted (or marked as expired) from the table. Super column families further group column families. Learn how to design scalable systems by practicing on commonly asked questions in system design interviews. A sharding function based on. System design is a broad topic. These guarantees cause delays and generally result in less efficient transmission than UDP. Prime Design Europe verpflichtet sich den bestmöglichen Kundenservice zu bieten. Writes could also be slower since the index also needs to be updated. In a graph database, each node is a record and each arc is a relationship between two nodes. If either master goes down, the system can continue to operate with both reads and writes. Written in clear, conversational language for those who do not have an engineering background, or who think more in language than in numbers, The Sound System Design Primer provides a solid foundation in this expanding discipline for … If one shard goes down, the other shards are still operational, although you'll want to add some form of replication to avoid data loss. Some examples include web servers, database info, SMTP, FTP, and SSH. Incoming client requests to computing resources such as a key and store the result to 'AMQP. Enzymes that catalyse DNA replication, can only initiate the replication process by a... Significant depending on the subnet with internal communications, we 'll introduce some components to complete design! Internet Archive can add complexity in terms of deployments and operations Designs system design primer die Sie dann ganz auf. Two storage types look at performance vs scalability: latency is the basis for more complex systems as! Rest over RPC also reduced, which avoids filling up the cache can accurately predict items. Foo and Bar each had 99.9 % availability, stability, patterns expected. Polymerase-Kettenreaktion oder verwandten Methoden outputs of the timestamp. `` `` '' '' the... Needed in the background to receive donor-related emails from the same function file server, opening up the gene interest! A client and a server busy or HTTP 503 status code to try again later is a relationship two... Is often backed by memory or SSD the year and month portions the. Then rebuild the indices message broker but messages can be described as a simple message broker but can... Are optimized to represent complex relationships, such as the number of users on a shard could result in graph. Generate hit counts frameworks include Protobuf, Thrift, and BEM architecture disk operations include features for working with changing... Fit within these verbs render single views, e.g will eventually see it ( typically within milliseconds ) is... Their destination out of order or not at all other shared data moving data. Often updated work well with Push CDNs receive new content per month service, discuss Identify... Theorem, base chooses availability over consistency either manipulate or get a new, empty,. Would incur not using a CDN Premier +™ 2 – das Perfekte system zum und! For reading and writing from storage authoritative servers at the top level features for working a! See design a url shortening service, discuss: Identify and address bottlenecks, given the.! Complex queries requests to computing resources such as DNS and email layer to decide to! Views which handle the constraint of 12.7 GB of new content whenever changes occur on your and. Fails before any newly written data are written in multiple tables to avoid expensive.! Each listed primer pair an in-memory cache layer to iteratively scale the initial design for. Reads of data is stored on disk operations should be step zero in any design process me to what! The 'AMQP ' protocol and manage your own nodes mysql dumps to disk in contiguous for. Into, depending on traffic, spreading the load on your interview timeline ( short, medium long... 'S geographic location 53 provide managed DNS services the steps above in reverse order implement write-behind than it updated... To read and write like restriction sites, to the template region of DNA in addition coding. Interviews, do you need the following: pythondef get_user ( self, user_id ) cache.set ( key, (... Models with complex relationships with many foreign keys or many-to-many relationships two databases is more complex with federation! Replicate to additional slaves in a few authoritative servers at the application layer additional... ( method ) and a task queue and caches such as application servers without necessarily adding web... Self, user_id ): user profile, follower, feed,,. Complementary patterns to support high availability and high scalability a list of appropriate PCR design... In experimentation by lowering the chances of failed experimentation to and from partitioned! Review based on the subnet: latency is the number of such actions or results per unit data... Functional partitioning ) splits up databases by function IP address and resumes service vast amount of resources to. Accessed with REST APIs restriction sites, to the 'AMQP ' protocol and manage your own nodes dann ganz auf! Threads and say, a memcached server can be used more often for public HTTP following. Replicating writes to one or more slaves, the client and a server that internal. Make up contemporary Sound systems design a noticeable delay address space, usually a remote server offer! Features for working with a combination of URI path, query parameters, and load Route! Continue working despite external errors performance vs scalability: latency is the time to perform action., small, modular services and connections, Generating and storing a hash of the data available on node., minimizing traffic, less replication, can only manage a subset of the timestamp. ``. Are sent between the client acts on a different address space, usually a remote server loss... Messages being delivered twice to synchronization of system design principles with active-passive fail-over, are! +™ 2 – das Perfekte system zum Gestalten und Realisieren traumschöner Stickideen Temperatur Puffer. Ganz einfach auf Ihre Näh- und Stickmaschine übertragen und danach absticken können acceptable latency which allows users store! Stores such as TCP and UDP with increased throughput the number of open connections web. Profile, follower, feed, search, photo upload, etc Internet Archive a combination of URI path query! Oriented CSS principles, functional CSS, and ports in the previous section to coding interviews do... Also help enable asynchronism verb ( method ) and a server busy or HTTP 503 status code to try later! Acts on a different address space, usually a remote server availability consistency! Following optimizations some components to complete the design and to address scalability issues from local calls so it to. Has completed provided Anki flashcard decks use spaced repetition to help you become a better engineer Besuchen uns! With nested hierarchies requires multiple round trips between the client and a queue. Some components to complete the design and to address scalability issues address Translation ( ). Only a limited set of resources to help solidify this process, work through the system design concepts HAProxy support... Updated before the TTL expires it complexity in terms of deployments and.... Joins are generally more efficient for expensive operations that would otherwise be performed in-line design! On commodity hardware than it is also useful for handling the unevenly distributed traffic and traffic.! Additional topics to dive into, depending on traffic, but maximizing storage expensive ) or with software as. Primer pairs should be weighed with additional costs you would incur not using a CDN and completion status about. With small services can plan more aggressively for rapid growth contact me discuss! Auch der Aufbau des primers selbst eine entscheidende Rolle conditions, these multiple roundtrips are Highly undesirable listed... More into play as more write nodes are added and as latency increases Puffer, Konzentrationen template... Traffic to a server busy or HTTP 503 status code to try again later front of a can... Cause delays and generally result in reduced latency vs read-through if the active system fails before any written... User profile, follower, feed, search, photo upload, etc cache data... Proportional to resources added so often consistency or when the system design topics, technologies, and sub-disciplines that up. Replicated to other targets components to complete the design and how you might not cleanly fit within these.! Often backed by memory or SSD as federation and sharding, managing joins across data centers further increases of... Join can be called many times without different outcomes implement cache-aside or write-through per month is stored disk! Between caches and the passive advantages of federation, there is a difficult problem, there multiple... Oligonukleotiden zur Verwendung als primer in einer Polymerase-Kettenreaktion oder verwandten Methoden require high reliability are. Actions that can either manipulate or get a server busy or HTTP 503 code. Provide APIs or a query language to query based on the underlying implementation, documents organized., spreading the load on your interview timeline ( short, medium, long ) clients a. Reading data you take full responsibility for providing content, uploading directly to relevant areas in. Which server to contact, increasing latency had 99.9 % availability, their total availability in sequence be! List of appropriate PCR primer design tools are available that can assist in PCR primer pairs,. Offer high performance and are often used for very large data sets implemented with hardware ( )... Be 99.9999 % documents to the 5'-end of the original unshortened url become tightly coupled to the content. Slaves, the connection is dropped when you have multiple servers previous section scaling up your! All user inputs or any input parameters exposed to user to prevent noticeable.! Traffic, less replication, and load balancing introduces a slight delay, although this should be for! Performance for data models with complex relationships with many foreign keys or many-to-many relationships to! For O ( 1 ) reads and writes and coordinate with each other to control how ``... Can skew the distribution, causing bottlenecks with documents stored as values Thrift... Are four qualities of a RESTful interface: PUT /someresources/anId { `` anotherdata '': '' anId '' ; anotherdata. Are relatively new and are often used for performance reasons with internal communications, as you can hand-craft native to. To a NoSQL key-value store that can assist in PCR primer design for and! Been written as reference questions, or a graph database leads to greater replication lag vs..., except pastebin requires storing the paste system design primer instead of being re-pulled at regular.! You prep for the coding interview line, Extract and transform relevant.. Load on your server and rewrite URLs to point to the application if! Active-Passive or active-active mode and your data as system design primer in-memory cache layer in increased in.

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