diff --git a/src/main/scala/gs/predicate/v0/json/JsonQueryIn.scala b/src/main/scala/gs/predicate/v0/json/JsonQueryIn.scala
new file mode 100644
index 0000000..46d93fd
--- /dev/null
+++ b/src/main/scala/gs/predicate/v0/json/JsonQueryIn.scala
@@ -0,0 +1,49 @@
+package gs.predicate.v0.json
+
+import cats.Applicative
+import cats.syntax.all.*
+import gs.predicate.v0.api.Predicate
+import gs.predicate.v0.json.query.JsonQuery
+import io.circe.Json
+
+/** Predicate that matches if the JSON provider contains a JSON blob with the
+  * given key, and that blob contains the given query, and the result of the
+  * query matches one of the given values.
+  *
+  * @param key
+  *   The name of the JSON value that must satisfy the given query.
+  * @param query
+  *   The [[JsonQuery]] that must be satisfied.
+  * @param values
+  *   The set of JSON values, such that one value should match the input.
+  */
+final class JsonQueryIn[F[_]: Applicative: JsonProvider](
+  val key: String,
+  val query: JsonQuery,
+  val values: Set[Json]
+) extends Predicate[F]:
+
+  /** @inheritDocs
+    */
+  final override val predicateType: String = JsonQueryIn.PredicateType
+
+  /** @inheritDocs
+    */
+  override def eval(): F[Predicate.Result] =
+    JsonProvider[F].get(key).map {
+      case None       => Predicate.Result.missed()
+      case Some(json) => Predicate.Result(query.eval(json, values.contains))
+    }
+
+object JsonQueryIn:
+
+  final val PredicateType: String = "json-query-in"
+
+  def apply[F[_]: Applicative: JsonProvider](
+    key: String,
+    query: JsonQuery,
+    values: Set[Json]
+  ): JsonQueryIn[F] =
+    new JsonQueryIn[F](key, query, values)
+
+end JsonQueryIn
diff --git a/src/main/scala/gs/predicate/v0/json/MemoryMapJsonProvider.scala b/src/main/scala/gs/predicate/v0/json/MemoryMapJsonProvider.scala
new file mode 100644
index 0000000..92a3aae
--- /dev/null
+++ b/src/main/scala/gs/predicate/v0/json/MemoryMapJsonProvider.scala
@@ -0,0 +1,20 @@
+package gs.predicate.v0.json
+
+import cats.effect.std.MapRef
+import io.circe.Json
+
+/** Provides keys and JSON values, given some in-memory map.
+  *
+  * @param map
+  *   The underlying map.
+  */
+final class MemoryMapJsonProvider[F[_]](
+  private val map: MapRef[F, String, Option[Json]]
+) extends JsonProvider[F]:
+
+  /** @inheritDocs
+    */
+  override def get(key: String): F[Option[Json]] =
+    map.apply(key).get
+
+end MemoryMapJsonProvider
diff --git a/src/test/scala/gs/predicate/v0/json/JsonQueryEqualsTests.scala b/src/test/scala/gs/predicate/v0/json/JsonQueryEqualsTests.scala
new file mode 100644
index 0000000..aece2b9
--- /dev/null
+++ b/src/test/scala/gs/predicate/v0/json/JsonQueryEqualsTests.scala
@@ -0,0 +1,128 @@
+package gs.predicate.v0.json
+
+import cats.effect.IO
+import cats.effect.std.MapRef
+import gs.datagen.v0.Gen
+import gs.datagen.v0.generators.Size
+import gs.predicate.v0.api.Predicate
+import gs.predicate.v0.json.query.JsonQuery
+import io.circe.Json
+import support.IOSuite
+
+class JsonQueryEqualsTests extends IOSuite:
+
+  import JsonQueryEqualsTests.Data
+  import JsonQueryEqualsTests.newProvider
+
+  iotest("should find an exact match against some string value") {
+    val key   = Data.keyGen.gen()
+    val value = Data.strValGen.gen()
+    val query = key
+    val blob  = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryEquals[IO](key, JsonQuery.compile(query), value)
+      p.eval().map(result => assertEquals(result, Predicate.Result.matched()))
+    }
+  }
+
+  iotest("should fail to match against some non-equal string value") {
+    val key         = Data.keyGen.gen()
+    val value       = Data.strValGen.gen()
+    val searchValue = Data.strValGen.gen()
+    val query       = key
+    val blob        = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryEquals[IO](key, JsonQuery.compile(query), searchValue)
+      p.eval().map(result => assertEquals(result, Predicate.Result.missed()))
+    }
+  }
+
+  iotest("should find an exact match against some integer value") {
+    val key   = Data.keyGen.gen()
+    val value = Data.intValGen.gen()
+    val query = key
+    val blob  = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryEquals[IO](key, JsonQuery.compile(query), value)
+      p.eval().map(result => assertEquals(result, Predicate.Result.matched()))
+    }
+  }
+
+  iotest("should fail to match against some non-equal integer value") {
+    val key         = Data.keyGen.gen()
+    val value       = Data.intValGen.gen()
+    val searchValue = Data.intValGen.gen()
+    val query       = key
+    val blob        = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryEquals[IO](key, JsonQuery.compile(query), searchValue)
+      p.eval().map(result => assertEquals(result, Predicate.Result.missed()))
+    }
+  }
+
+  iotest("should find an exact match against some boolean value") {
+    val key   = Data.keyGen.gen()
+    val value = Data.boolValGen.gen()
+    val query = key
+    val blob  = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryEquals[IO](key, JsonQuery.compile(query), value)
+      p.eval().map(result => assertEquals(result, Predicate.Result.matched()))
+    }
+  }
+
+  iotest("should fail to match against some non-equal boolean value") {
+    val key         = Data.keyGen.gen()
+    val value       = Json.fromBoolean(true)
+    val searchValue = Json.fromBoolean(false)
+    val query       = key
+    val blob        = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryEquals[IO](key, JsonQuery.compile(query), searchValue)
+      p.eval().map(result => assertEquals(result, Predicate.Result.missed()))
+    }
+  }
+
+object JsonQueryEqualsTests:
+
+  object Data:
+
+    val keyGen: Gen[String] = Gen.string.alphaNumeric(Size.between(4, 16))
+
+    val strValGen: Gen[Json] =
+      Gen.string.uppercaseAlpha(Size.fixed(8)).map(Json.fromString)
+
+    val intValGen: Gen[Json]  = Gen.integer.inRange(0, 1000).map(Json.fromInt)
+    val boolValGen: Gen[Json] = Gen.boolean().map(Json.fromBoolean)
+
+  end Data
+
+  def newProvider(data: Map[String, Json]): IO[JsonProvider[IO]] =
+    for map <- MapRef.ofSingleImmutableMap[IO, String, Json](data)
+    yield new MemoryMapJsonProvider(map)
+
+end JsonQueryEqualsTests
diff --git a/src/test/scala/gs/predicate/v0/json/JsonQueryInTests.scala b/src/test/scala/gs/predicate/v0/json/JsonQueryInTests.scala
new file mode 100644
index 0000000..8c886f3
--- /dev/null
+++ b/src/test/scala/gs/predicate/v0/json/JsonQueryInTests.scala
@@ -0,0 +1,68 @@
+package gs.predicate.v0.json
+
+import cats.effect.IO
+import cats.effect.std.MapRef
+import gs.datagen.v0.Gen
+import gs.datagen.v0.generators.Size
+import gs.predicate.v0.api.Predicate
+import gs.predicate.v0.json.query.JsonQuery
+import io.circe.Json
+import support.IOSuite
+
+class JsonQueryInTests extends IOSuite:
+
+  import JsonQueryInTests.Data
+  import JsonQueryInTests.newProvider
+
+  iotest("should find an exact match against some set of values") {
+    val key    = Data.keyGen.gen()
+    val value  = Data.strValGen.gen()
+    val values = Set(value, Data.strValGen.gen(), Data.intValGen.gen())
+    val query  = key
+    val blob   = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryIn[IO](key, JsonQuery.compile(query), values)
+      p.eval().map(result => assertEquals(result, Predicate.Result.matched()))
+    }
+  }
+
+  iotest("should fail to match anything within some set of values") {
+    val key          = Data.keyGen.gen()
+    val value        = Data.strValGen.gen()
+    val searchValues = Set(Data.strValGen.gen())
+    val query        = key
+    val blob         = Json.obj(
+      key -> value
+    )
+
+    newProvider(Map(key -> blob)).flatMap { provider =>
+      given JsonProvider[IO] = provider
+      val p = JsonQueryIn[IO](key, JsonQuery.compile(query), searchValues)
+      p.eval().map(result => assertEquals(result, Predicate.Result.missed()))
+    }
+  }
+
+end JsonQueryInTests
+
+object JsonQueryInTests:
+
+  object Data:
+
+    val keyGen: Gen[String] = Gen.string.alphaNumeric(Size.between(4, 16))
+
+    val strValGen: Gen[Json] =
+      Gen.string.uppercaseAlpha(Size.fixed(8)).map(Json.fromString)
+
+    val intValGen: Gen[Json] = Gen.integer.inRange(0, 1000).map(Json.fromInt)
+
+  end Data
+
+  def newProvider(data: Map[String, Json]): IO[JsonProvider[IO]] =
+    for map <- MapRef.ofSingleImmutableMap[IO, String, Json](data)
+    yield new MemoryMapJsonProvider(map)
+
+end JsonQueryInTests
diff --git a/src/test/scala/gs/predicate/v0/kv/ValueInTests.scala b/src/test/scala/gs/predicate/v0/kv/ValueInTests.scala
new file mode 100644
index 0000000..538df2f
--- /dev/null
+++ b/src/test/scala/gs/predicate/v0/kv/ValueInTests.scala
@@ -0,0 +1,66 @@
+package gs.predicate.v0.kv
+
+import cats.effect.IO
+import cats.effect.std.MapRef
+import gs.datagen.v0.Gen
+import gs.datagen.v0.generators.Size
+import gs.predicate.v0.api.Predicate
+import support.IOSuite
+
+class ValueInTests extends IOSuite:
+
+  import ValueInTests.Data
+
+  iotest("should find an exact match against some value") {
+    ValueInTests.newProvider(Data.KeyValues).flatMap { provider =>
+      given KeyValueProvider[IO] = provider
+      val p                      =
+        ValueIn[IO](
+          Data.ExistingKey,
+          Set(
+            Data.ExistingValue,
+            "",
+            Gen.string.alphaNumeric(Size.Fixed(8)).gen()
+          )
+        )
+      for result <- p.eval()
+      yield assertEquals(result, Predicate.Result.matched())
+    }
+  }
+
+  iotest("should not find a value if it is not associated to a key") {
+    ValueInTests.newProvider(Data.KeyValues).flatMap { provider =>
+      given KeyValueProvider[IO] = provider
+      val p                      =
+        ValueIn[IO](Data.ExistingKey, Set(Data.NotExistingValue))
+      for result <- p.eval()
+      yield assertEquals(result, Predicate.Result.missed())
+    }
+  }
+
+  iotest("should not find a key that does not exist within some provider") {
+    ValueInTests.newProvider(Data.KeyValues).flatMap { provider =>
+      given KeyValueProvider[IO] = provider
+      val p                      = ValueIn[IO](Data.NotExistingKey, Set(""))
+      for result <- p.eval()
+      yield assertEquals(result, Predicate.Result.missed())
+    }
+  }
+
+object ValueInTests:
+
+  object Data:
+
+    val ExistingKey: String      = Gen.string.alphaNumeric(Size.Fixed(8)).gen()
+    val NotExistingKey: String   = Gen.string.alphaNumeric(Size.Fixed(6)).gen()
+    val ExistingValue: String    = Gen.string.alphaNumeric(Size.Fixed(10)).gen()
+    val NotExistingValue: String = Gen.string.alphaNumeric(Size.Fixed(4)).gen()
+    val KeyValues: Map[String, String] = Map(ExistingKey -> ExistingValue)
+
+  end Data
+
+  def newProvider(data: Map[String, String]): IO[KeyValueProvider[IO]] =
+    for map <- MapRef.ofSingleImmutableMap[IO, String, String](data)
+    yield new MemoryMapKeyValueProvider(map)
+
+end ValueInTests