diff --git a/build.sbt b/build.sbt
index 1277317..3f2f57e 100644
--- a/build.sbt
+++ b/build.sbt
@@ -31,6 +31,7 @@ lazy val root = project.in(file("."))
       Dependencies.Libraries.catsEffect,
       Dependencies.Libraries.circeParser,
       Dependencies.Libraries.lruMap,
+      Dependencies.Libraries.scalaj,
       Dependencies.Libraries.specs2Core,
       Dependencies.Libraries.specs2Mock
     )
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index df6ae5b..a81457a 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -32,16 +32,17 @@ object Dependencies {
 
   object Libraries {
     // Java
-    val jodaMoney    = "org.joda"              % "joda-money"         % V.jodaMoney
-    val jodaConvert  = "org.joda"              % "joda-convert"       % V.jodaConvert
+    val jodaMoney    = "org.joda"              % "joda-money"     % V.jodaMoney
+    val jodaConvert  = "org.joda"              % "joda-convert"   % V.jodaConvert
 
     // Scala
-    val catsEffect   = "org.typelevel"         %% "cats-effect"       % V.catsEffect
-    val circeParser  = "io.circe"              %% "circe-parser"      % V.circe
-    val lruMap       = "com.snowplowanalytics" %% "scala-lru-map"     % V.lruMap
+    val catsEffect   = "org.typelevel"         %% "cats-effect"   % V.catsEffect
+    val circeParser  = "io.circe"              %% "circe-parser"  % V.circe
+    val lruMap       = "com.snowplowanalytics" %% "scala-lru-map" % V.lruMap
+    val scalaj       = "org.scalaj"            %% "scalaj-http"   % V.scalaj
 
     // Scala (test only)
-    val specs2Core   = "org.specs2"            %% "specs2-core"       % V.specs2        % "test"
-    val specs2Mock   = "org.specs2"            %% "specs2-mock"       % V.specs2        % "test"
+    val specs2Core   = "org.specs2"            %% "specs2-core"   % V.specs2     % "test"
+    val specs2Mock   = "org.specs2"            %% "specs2-mock"   % V.specs2     % "test"
   }
 }
diff --git a/src/main/scala/com.snowplowanalytics/forex/Forex.scala b/src/main/scala/com.snowplowanalytics/forex/Forex.scala
index d031607..1e96d99 100644
--- a/src/main/scala/com.snowplowanalytics/forex/Forex.scala
+++ b/src/main/scala/com.snowplowanalytics/forex/Forex.scala
@@ -23,7 +23,8 @@ import cats.implicits._
 import cats.data.{EitherT, OptionT}
 import org.joda.money._
 
-import oerclient._
+import errors._
+import model._
 
 /** Companion object to get Forex object */
 object Forex {
@@ -48,7 +49,7 @@ object Forex {
     }
 
   def getForex[F[_]: Sync](config: ForexConfig): F[Forex[F]] =
-    ForexClient
+    OerClient
       .getClient[F](config)
       .map(client => Forex(config, client))
 }
@@ -62,7 +63,7 @@ object Forex {
  * @param config A configurator for Forex object
  * @param client Passed down client that does actual work
  */
-case class Forex[F[_]](config: ForexConfig, client: ForexClient[F]) {
+case class Forex[F[_]](config: ForexConfig, client: OerClient[F]) {
 
   def rate: ForexLookupTo[F] = ForexLookupTo(1, config.baseCurrency, config, client)
 
@@ -110,7 +111,7 @@ case class ForexLookupTo[F[_]](
   conversionAmount: Double,
   fromCurr: CurrencyUnit,
   config: ForexConfig,
-  client: ForexClient[F]
+  client: OerClient[F]
 ) {
 
   /**
@@ -136,7 +137,7 @@ case class ForexLookupWhen[F[_]: Sync](
   fromCurr: CurrencyUnit,
   toCurr: CurrencyUnit,
   config: ForexConfig,
-  client: ForexClient[F]
+  client: OerClient[F]
 ) {
   // convert `conversionAmt` into BigDecimal representation for its later usage in BigMoney
   val conversionAmt = new BigDecimal(conversionAmount)
diff --git a/src/main/scala/com.snowplowanalytics/forex/ForexClient.scala b/src/main/scala/com.snowplowanalytics/forex/ForexClient.scala
deleted file mode 100644
index 2f57896..0000000
--- a/src/main/scala/com.snowplowanalytics/forex/ForexClient.scala
+++ /dev/null
@@ -1,91 +0,0 @@
-/*
- * Copyright (c) 2013-2018 Snowplow Analytics Ltd. All rights reserved.
- *
- * This program is licensed to you under the Apache License Version 2.0,
- * and you may not use this file except in compliance with the Apache License Version 2.0.
- * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the Apache License Version 2.0 is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
- */
-package com.snowplowanalytics.forex
-
-import java.time.ZonedDateTime
-
-import cats.effect.Sync
-import cats.syntax.apply._
-import cats.syntax.functor._
-import cats.syntax.option._
-import org.joda.money.CurrencyUnit
-
-import com.snowplowanalytics.lrumap.CreateLruMap
-import oerclient._
-
-/**
- * Companion object for ForexClient class
- * This class has one method for getting forex clients
- * but for now there is only one client since we are only using OER
- */
-object ForexClient {
-
-  /** Creates a client with a cache and sensible default ForexConfig */
-  def getClient[F[_]: Sync](appId: String, accountLevel: AccountType): F[ForexClient[F]] =
-    getClient[F](ForexConfig(appId = appId, accountLevel = accountLevel))
-
-  /** Getter for clients, creating the caches as defined in the config */
-  def getClient[F[_]: Sync](
-    config: ForexConfig
-  )(
-    implicit CLM1: CreateLruMap[F, NowishCacheKey, NowishCacheValue],
-    CLM2: CreateLruMap[F, EodCacheKey, EodCacheValue]
-  ): F[ForexClient[F]] = {
-    val nowishCacheF =
-      if (config.nowishCacheSize > 0) {
-        CLM1.create(config.nowishCacheSize).map(_.some)
-      } else {
-        Sync[F].pure(Option.empty[NowishCache[F]])
-      }
-
-    val eodCacheF =
-      if (config.eodCacheSize > 0) {
-        CLM2.create(config.eodCacheSize).map(_.some)
-      } else {
-        Sync[F].pure(Option.empty[EodCache[F]])
-      }
-
-    (nowishCacheF, eodCacheF).mapN {
-      case (nowish, eod) =>
-        new OerClient[F](config, nowishCache = nowish, eodCache = eod)
-    }
-  }
-
-  def getClient[F[_]: Sync](
-    config: ForexConfig,
-    nowishCache: Option[NowishCache[F]],
-    eodCache: Option[EodCache[F]]
-  ): ForexClient[F] = new OerClient[F](config, nowishCache, eodCache)
-}
-
-abstract class ForexClient[F[_]](
-  val config: ForexConfig,
-  val nowishCache: Option[NowishCache[F]] = None,
-  val eodCache: Option[EodCache[F]]       = None
-) {
-
-  /**
-   * Get the latest exchange rate from a given currency
-   * @param currency Desired currency
-   * @return result returned from API
-   */
-  def getLiveCurrencyValue(currency: CurrencyUnit): F[ApiRequestResult]
-
-  /**
-   * Get a historical exchange rate from a given currency and date
-   * @param currency Desired currency
-   * @param date Date of desired rate
-   * @return result returned from API
-   */
-  def getHistoricalCurrencyValue(currency: CurrencyUnit, date: ZonedDateTime): F[ApiRequestResult]
-}
diff --git a/src/main/scala/com.snowplowanalytics/forex/ForexConfig.scala b/src/main/scala/com.snowplowanalytics/forex/ForexConfig.scala
deleted file mode 100644
index b224b66..0000000
--- a/src/main/scala/com.snowplowanalytics/forex/ForexConfig.scala
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
- * Copyright (c) 2013-2018 Snowplow Analytics Ltd. All rights reserved.
- *
- * This program is licensed to you under the Apache License Version 2.0,
- * and you may not use this file except in compliance with the Apache License Version 2.0.
- * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the Apache License Version 2.0 is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
- */
-package com.snowplowanalytics.forex
-
-import org.joda.money.CurrencyUnit
-
-/** User defined type for getNearestDay flag */
-sealed trait EodRounding
-
-/** Round to previous day*/
-object EodRoundDown extends EodRounding
-
-/** Round to next day*/
-object EodRoundUp extends EodRounding
-
-/**
- * There are three types of accounts supported by OER API.
- * For scala-forex library, the main difference between Unlimited/Enterprise
- * and Developer users is that users with Unlimited/Enterprise accounts
- * can use the base currency for API requests, but this library will provide
- * automatic conversions between OER default base currencies(USD)
- * and user-defined base currencies. However this will increase calls to the API
- * and will slow down the performance.
- */
-sealed trait AccountType
-object DeveloperAccount extends AccountType
-object EnterpriseAccount extends AccountType
-object UnlimitedAccount extends AccountType
-
-/**
- * Configure class for Forex object
- * @param appId Key for the api
- * @param accountLevel Type of the registered account
- * @param nowishCacheSize Cache for nowish look up
- * @param nowishSecs Time range for nowish look up
- * @param eodCacheSize Cache for historical lookup
- * @param getNearestDay Flag for deciding whether to get the exchange rate on closer day or previous day
- * @param baseCurrency Base currency is set to be USD by default if configurableBase flag is false, otherwise it is user-defined
- */
-case class ForexConfig(
-  /**
-   * Register an account on https://openexchangerates.org to obtain your unique key
-   */
-  appId: String,
-  accountLevel: AccountType,
-  /**
-   * nowishCacheSize = (165 * 164 / 2) = 13530.
-   * There are 165 currencies in total, the combinations of a currency pair
-   * has 165 * (165 - 1) possibilities. (X,Y) is the same as (Y,X) hence 165 * 164 / 2
-   */
-  nowishCacheSize: Int = 13530,
-  /** 5 mins by default */
-  nowishSecs: Int = 300,
-  /** 165 * 164 / 2 * 30 = 405900, assuming the cache stores data within a month */
-  eodCacheSize: Int          = 405900,
-  getNearestDay: EodRounding = EodRoundDown,
-  baseCurrency: CurrencyUnit = CurrencyUnit.USD
-)
diff --git a/src/main/scala/com.snowplowanalytics/forex/oerclient/OerClient.scala b/src/main/scala/com.snowplowanalytics/forex/OerClient.scala
similarity index 77%
rename from src/main/scala/com.snowplowanalytics/forex/oerclient/OerClient.scala
rename to src/main/scala/com.snowplowanalytics/forex/OerClient.scala
index 80a4669..948b114 100644
--- a/src/main/scala/com.snowplowanalytics/forex/oerclient/OerClient.scala
+++ b/src/main/scala/com.snowplowanalytics/forex/OerClient.scala
@@ -11,35 +11,19 @@
  * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
  */
 package com.snowplowanalytics.forex
-package oerclient
 
-import java.net.URL
-import java.net.HttpURLConnection
 import java.time.{LocalDateTime, ZoneId, ZonedDateTime}
 import java.math.{BigDecimal => JBigDecimal}
 
-import scala.util.Try
-
 import cats.effect.Sync
 import cats.implicits._
 import cats.data.EitherT
-import io.circe._
-import io.circe.parser.parse
 import org.joda.money.CurrencyUnit
 
-object OerClient {
-  final case class OerResponse(rates: Map[CurrencyUnit, BigDecimal])
-
-  // Encoder ignores Currencies that are not parsable by CurrencyUnit
-  implicit val oerResponseDecoder = new Decoder[OerResponse] {
-    override def apply(c: HCursor): Decoder.Result[OerResponse] =
-      c.downField("rates").as[Map[String, BigDecimal]].map { map =>
-        OerResponse(
-          map.toList.mapFilter { case (key, value) => Try(CurrencyUnit.of(key)).toOption.map(_ -> value) }.toMap)
-      }
-  }
-
-}
+import com.snowplowanalytics.lrumap.CreateLruMap
+import errors._
+import model._
+import responses._
 
 /**
  * Implements Json for Open Exchange Rates(http://openexchangerates.org)
@@ -47,16 +31,14 @@ object OerClient {
  * @param nowishCache - user defined nowishCache
  * @param eodCache - user defined eodCache
  */
-class OerClient[F[_]: Sync](
+case class OerClient[F[_]: Sync](
   config: ForexConfig,
-  nowishCache: Option[NowishCache[F]] = None,
-  eodCache: Option[EodCache[F]]       = None
-) extends ForexClient[F](config, nowishCache, eodCache) {
-
-  import OerClient._
+  val nowishCache: Option[NowishCache[F]] = None,
+  val eodCache: Option[EodCache[F]]       = None,
+  transport: Transport[F]
+) {
 
-  /** Base URL to OER API */
-  private val oerUrl = "http://openexchangerates.org/api/"
+  private val endpoint = "openexchangerates.org/api/"
 
   /** Sets the base currency in the url
    * according to the API, only Unlimited and Enterprise accounts
@@ -88,7 +70,7 @@ class OerClient[F[_]: Sync](
    */
   def getLiveCurrencyValue(currency: CurrencyUnit): F[ApiRequestResult] = {
     val action = for {
-      response     <- EitherT(getResponseFromApi(latest))
+      response     <- EitherT(transport.receive(endpoint, latest))
       liveCurrency <- EitherT(extractLiveCurrency(response, currency))
     } yield liveCurrency
     action.value
@@ -167,7 +149,7 @@ class OerClient[F[_]: Sync](
     } else {
       val historicalLink = buildHistoricalLink(date)
       val action = for {
-        response <- EitherT(getResponseFromApi(historicalLink))
+        response <- EitherT(transport.receive(endpoint, historicalLink))
         currency <- EitherT(extractHistoricalCurrency(response, currency, date))
       } yield currency
 
@@ -220,32 +202,50 @@ class OerClient[F[_]: Sync](
           .map(_.bigDecimal)
           .toRight(OerResponseError(s"Currency not found in the API, invalid currency $currency", IllegalCurrency)))
   }
+}
 
-  /**
-   * Helper method which returns the node containing
-   * a list of currency and rate pair.
-   * @param downloadPath - The URI link for the API request
-   * @return JSON node which contains currency information obtained from API
-   * or OerResponseError object which carries the error message returned by the API
-   */
-  private def getResponseFromApi(downloadPath: String): F[Either[OerResponseError, OerResponse]] =
-    Sync[F].delay {
-      val url  = new URL(oerUrl + downloadPath)
-      val conn = url.openConnection
-      conn match {
-        case httpUrlConn: HttpURLConnection =>
-          if (httpUrlConn.getResponseCode >= 400) {
-            val errorString = scala.io.Source.fromInputStream(httpUrlConn.getErrorStream).mkString
-            parse(errorString)
-              .flatMap(_.hcursor.downField("message").as[String])
-              .leftMap(e => OerResponseError(e.getMessage, OtherErrors))
-              .flatMap(message => Left(OerResponseError(message, OtherErrors)))
-          } else {
-            parse(scala.io.Source.fromInputStream(httpUrlConn.getInputStream).mkString)
-              .flatMap(_.as[OerResponse])
-              .leftMap(e => OerResponseError(e.getMessage, OtherErrors))
-          }
-        case _ => throw new ClassCastException
+/**
+ * Companion object for ForexClient class
+ * This class has one method for getting forex clients
+ * but for now there is only one client since we are only using OER
+ */
+object OerClient {
+
+  /** Creates a client with a cache and sensible default ForexConfig */
+  def getClient[F[_]: Sync](appId: String, accountLevel: AccountType): F[OerClient[F]] =
+    getClient[F](ForexConfig(appId = appId, accountLevel = accountLevel))
+
+  /** Getter for clients, creating the caches as defined in the config */
+  def getClient[F[_]: Sync](
+    config: ForexConfig
+  )(
+    implicit CLM1: CreateLruMap[F, NowishCacheKey, NowishCacheValue],
+    CLM2: CreateLruMap[F, EodCacheKey, EodCacheValue]
+  ): F[OerClient[F]] = {
+    val nowishCacheF =
+      if (config.nowishCacheSize > 0) {
+        CLM1.create(config.nowishCacheSize).map(_.some)
+      } else {
+        Sync[F].pure(Option.empty[NowishCache[F]])
       }
+
+    val eodCacheF =
+      if (config.eodCacheSize > 0) {
+        CLM2.create(config.eodCacheSize).map(_.some)
+      } else {
+        Sync[F].pure(Option.empty[EodCache[F]])
+      }
+
+    (nowishCacheF, eodCacheF).mapN {
+      case (nowish, eod) =>
+        new OerClient[F](config, nowishCache = nowish, eodCache = eod, Transport.httpTransport[F])
     }
+  }
+
+  def getClient[F[_]: Sync](
+    config: ForexConfig,
+    nowishCache: Option[NowishCache[F]],
+    eodCache: Option[EodCache[F]],
+    transport: Transport[F]
+  ): OerClient[F] = new OerClient[F](config, nowishCache, eodCache, transport)
 }
diff --git a/src/main/scala/com.snowplowanalytics/forex/Transport.scala b/src/main/scala/com.snowplowanalytics/forex/Transport.scala
new file mode 100644
index 0000000..8c47f1d
--- /dev/null
+++ b/src/main/scala/com.snowplowanalytics/forex/Transport.scala
@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2015-2019 Snowplow Analytics Ltd. All rights reserved.
+ *
+ * This program is licensed to you under the Apache License Version 2.0,
+ * and you may not use this file except in compliance with the Apache License Version 2.0.
+ * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the Apache License Version 2.0 is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
+ */
+package com.snowplowanalytics.forex
+
+import cats.Eval
+import cats.effect.Sync
+import cats.syntax.either._
+import io.circe.Decoder
+import io.circe.parser._
+import scalaj.http._
+
+import errors._
+import responses._
+
+trait Transport[F[_]] {
+
+  /**
+   * Main client logic for Request => Response function,
+   * where Response is wrapped in tparam `F`
+   * @param endpoint endpoint to interrogate
+   * @param path path to request
+   * @return extracted either error or exchanged rate wrapped in `F`
+   */
+  def receive(endpoint: String, path: String): F[Either[OerResponseError, OerResponse]]
+
+}
+
+object Transport {
+
+  /**
+   * Http Transport leveraging cats-effect's Sync.
+   * @return a Sync Transport
+   */
+  implicit def httpTransport[F[_]: Sync]: Transport[F] = new Transport[F] {
+    def receive(endpoint: String, path: String): F[Either[OerResponseError, OerResponse]] =
+      Sync[F].delay(buildRequest(endpoint, path))
+  }
+
+  /**
+   * Eval http Transport to use in cases where you have to do side-effects (e.g. spark or beam).
+   * @return an Eval Transport
+   */
+  implicit def evalHttpTransport: Transport[Eval] = new Transport[Eval] {
+    def receive(endpoint: String, path: String): Eval[Either[OerResponseError, OerResponse]] =
+      Eval.later {
+        buildRequest(endpoint, path)
+      }
+  }
+
+  implicit def eitherDecoder: Decoder[Either[OerResponseError, OerResponse]] =
+    implicitly[Decoder[OerResponseError]].either(implicitly[Decoder[OerResponse]])
+
+  private def buildRequest(
+    endpoint: String,
+    path: String
+  ): Either[OerResponseError, OerResponse] =
+    for {
+      response <- Http("http://" + endpoint + path).asString.body.asRight
+      parsed <- parse(response)
+        .leftMap(e => OerResponseError(s"OER response is not JSON: ${e.getMessage}", OtherErrors))
+      decoded <- parsed
+        .as[Either[OerResponseError, OerResponse]]
+        .leftMap(_ => OerResponseError(s"OER response couldn't be decoded", OtherErrors))
+      res <- decoded
+    } yield res
+}
diff --git a/src/main/scala/com.snowplowanalytics/forex/errors.scala b/src/main/scala/com.snowplowanalytics/forex/errors.scala
new file mode 100644
index 0000000..0280ace
--- /dev/null
+++ b/src/main/scala/com.snowplowanalytics/forex/errors.scala
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2013-2018 Snowplow Analytics Ltd. All rights reserved.
+ *
+ * This program is licensed to you under the Apache License Version 2.0,
+ * and you may not use this file except in compliance with the Apache License Version 2.0.
+ * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the Apache License Version 2.0 is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
+ */
+package com.snowplowanalytics.forex
+
+import io.circe.Decoder
+
+object errors {
+
+  /**
+   * OER error states from the HTTP requests
+   * @param errorMessage - error message from OER API
+   * @param errorType - specific error type
+   */
+  final case class OerResponseError(errorMessage: String, errorType: OerError)
+
+  implicit val oerResponseErrorDecoder: Decoder[OerResponseError] = Decoder.decodeString
+    .prepare(_.downField("message"))
+    .map(OerResponseError(_, OtherErrors))
+
+  /**
+   * User defined error types
+   */
+  sealed trait OerError
+
+  /**
+   * Caused by invalid DateTime argument
+   * i.e. either earlier than the earliest date OER service is available or later than currenct time
+   */
+  object ResourcesNotAvailable extends OerError
+
+  /**
+   * Currency not supported by API or
+   * Joda Money or both
+   */
+  object IllegalCurrency extends OerError
+
+  /**
+   * Other possible error types e.g.
+   * access permissions
+   */
+  object OtherErrors extends OerError
+}
diff --git a/src/main/scala/com.snowplowanalytics/forex/model.scala b/src/main/scala/com.snowplowanalytics/forex/model.scala
new file mode 100644
index 0000000..9f688ae
--- /dev/null
+++ b/src/main/scala/com.snowplowanalytics/forex/model.scala
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2013-2018 Snowplow Analytics Ltd. All rights reserved.
+ *
+ * This program is licensed to you under the Apache License Version 2.0,
+ * and you may not use this file except in compliance with the Apache License Version 2.0.
+ * You may obtain a copy of the Apache License Version 2.0 at http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the Apache License Version 2.0 is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
+ */
+package com.snowplowanalytics.forex
+
+import org.joda.money.CurrencyUnit
+
+object model {
+
+  /** User defined type for getNearestDay flag */
+  sealed trait EodRounding
+
+  /** Round to previous day*/
+  object EodRoundDown extends EodRounding
+
+  /** Round to next day*/
+  object EodRoundUp extends EodRounding
+
+  /**
+   * There are three types of accounts supported by OER API.
+   * For scala-forex library, the main difference between Unlimited/Enterprise
+   * and Developer users is that users with Unlimited/Enterprise accounts
+   * can use the base currency for API requests, but this library will provide
+   * automatic conversions between OER default base currencies(USD)
+   * and user-defined base currencies. However this will increase calls to the API
+   * and will slow down the performance.
+   */
+  sealed trait AccountType
+  object DeveloperAccount extends AccountType
+  object EnterpriseAccount extends AccountType
+  object UnlimitedAccount extends AccountType
+
+  /**
+   * Configure class for Forex object
+   * @param appId Key for the api
+   * @param accountLevel Type of the registered account
+   * @param endpoint API endpoint
+   * @param nowishCacheSize Cache for nowish look up
+   * @param nowishSecs Time range for nowish look up
+   * @param eodCacheSize Cache for historical lookup
+   * @param getNearestDay Flag for deciding whether to get the exchange rate on closer day or previous day
+   * @param baseCurrency Base currency is set to be USD by default if configurableBase flag is false, otherwise it is user-defined
+   */
+  case class ForexConfig(
+    //  Register an account on https://openexchangerates.org to obtain your unique key
+    appId: String,
+    accountLevel: AccountType,
+    // nowishCacheSize = (165 * 164 / 2) = 13530.
+    // There are 165 currencies in total, the combinations of a currency pair
+    // has 165 * (165 - 1) possibilities. (X,Y) is the same as (Y,X) hence 165 * 164 / 2
+    nowishCacheSize: Int = 13530,
+    //5 mins by default
+    nowishSecs: Int = 300,
+    // 165 * 164 / 2 * 30 = 405900, assuming the cache stores data within a month
+    eodCacheSize: Int          = 405900,
+    getNearestDay: EodRounding = EodRoundDown,
+    baseCurrency: CurrencyUnit = CurrencyUnit.USD
+  )
+}
diff --git a/src/main/scala/com.snowplowanalytics/package.scala b/src/main/scala/com.snowplowanalytics/forex/package.scala
similarity index 97%
rename from src/main/scala/com.snowplowanalytics/package.scala
rename to src/main/scala/com.snowplowanalytics/forex/package.scala
index bb7e703..0df3deb 100644
--- a/src/main/scala/com.snowplowanalytics/package.scala
+++ b/src/main/scala/com.snowplowanalytics/forex/package.scala
@@ -18,7 +18,7 @@ import java.math.BigDecimal
 import org.joda.money.CurrencyUnit
 
 import com.snowplowanalytics.lrumap.LruMap
-import forex.oerclient.OerResponseError
+import forex.errors._
 
 package object forex {
 
diff --git a/src/main/scala/com.snowplowanalytics/forex/oerclient/OerResponseError.scala b/src/main/scala/com.snowplowanalytics/forex/responses.scala
similarity index 51%
rename from src/main/scala/com.snowplowanalytics/forex/oerclient/OerResponseError.scala
rename to src/main/scala/com.snowplowanalytics/forex/responses.scala
index e719182..d44c44e 100644
--- a/src/main/scala/com.snowplowanalytics/forex/oerclient/OerResponseError.scala
+++ b/src/main/scala/com.snowplowanalytics/forex/responses.scala
@@ -11,34 +11,26 @@
  * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
  */
 package com.snowplowanalytics.forex
-package oerclient
 
-/**
- * OER error states from the HTTP requests
- * @param errorMessage - error message from OER API
- * @param errorType - specific error type
- */
-case class OerResponseError(errorMessage: String, errorType: OerError)
-
-/**
- * User defined error types
- */
-sealed trait OerError
+import scala.util.Try
 
-/**
- * Caused by invalid DateTime argument
- * i.e. either earlier than the earliest date OER service is available or later than currenct time
- */
-object ResourcesNotAvailable extends OerError
+import cats.instances.list._
+import cats.syntax.functorFilter._
+import io.circe._
+import org.joda.money.CurrencyUnit
 
-/**
- * Currency not supported by API or
- * Joda Money or both
- */
-object IllegalCurrency extends OerError
+object responses {
+  final case class OerResponse(rates: Map[CurrencyUnit, BigDecimal])
 
-/**
- * Other possible error types e.g.
- * access permissions
- */
-object OtherErrors extends OerError
+  // Encoder ignores Currencies that are not parsable by CurrencyUnit
+  implicit val oerResponseDecoder: Decoder[OerResponse] = new Decoder[OerResponse] {
+    override def apply(c: HCursor): Decoder.Result[OerResponse] =
+      c.downField("rates").as[Map[String, BigDecimal]].map { map =>
+        OerResponse(
+          map.toList.mapFilter {
+            case (key, value) => Try(CurrencyUnit.of(key)).toOption.map(_ -> value)
+          }.toMap
+        )
+      }
+  }
+}
diff --git a/src/test/scala/com.snowplowanalytics.forex/ForexAtSpec.scala b/src/test/scala/com.snowplowanalytics.forex/ForexAtSpec.scala
index 098c240..260b556 100644
--- a/src/test/scala/com.snowplowanalytics.forex/ForexAtSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/ForexAtSpec.scala
@@ -18,6 +18,8 @@ import cats.effect.IO
 import org.joda.money.{CurrencyUnit, Money}
 import org.specs2.mutable.Specification
 
+import model._
+
 /**
  * Testing method for getting the latest end-of-day rate
  * prior to the datetime or the day after according to the user's setting
diff --git a/src/test/scala/com.snowplowanalytics.forex/ForexEodSpec.scala b/src/test/scala/com.snowplowanalytics.forex/ForexEodSpec.scala
index 878c0f4..7eb5e5f 100644
--- a/src/test/scala/com.snowplowanalytics.forex/ForexEodSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/ForexEodSpec.scala
@@ -20,6 +20,8 @@ import org.joda.money.{CurrencyUnit, Money}
 import org.specs2.mutable.Specification
 import org.specs2.matcher.DataTables
 
+import model._
+
 /**
  * Testing method for getting the end-of-date exchange rate
  * since historical forex rate is fixed, the actual look up result should be
diff --git a/src/test/scala/com.snowplowanalytics.forex/ForexNowSpec.scala b/src/test/scala/com.snowplowanalytics.forex/ForexNowSpec.scala
index ba1d7b4..f9f98f2 100644
--- a/src/test/scala/com.snowplowanalytics.forex/ForexNowSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/ForexNowSpec.scala
@@ -18,6 +18,8 @@ import cats.effect.IO
 import org.joda.money._
 import org.specs2.mutable.Specification
 
+import model._
+
 /** Testing method for getting the live exchange rate */
 class ForexNowSpec extends Specification {
   args(skipAll = sys.env.get("OER_KEY").isEmpty)
diff --git a/src/test/scala/com.snowplowanalytics.forex/ForexNowishSpec.scala b/src/test/scala/com.snowplowanalytics.forex/ForexNowishSpec.scala
index b8bdb1a..2e99f74 100644
--- a/src/test/scala/com.snowplowanalytics.forex/ForexNowishSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/ForexNowishSpec.scala
@@ -18,6 +18,8 @@ import cats.effect.IO
 import org.joda.money._
 import org.specs2.mutable.Specification
 
+import model._
+
 /** Testing method for getting the approximate exchange rate */
 class ForexNowishSpec extends Specification {
   args(skipAll = sys.env.get("OER_KEY").isEmpty)
diff --git a/src/test/scala/com.snowplowanalytics.forex/ForexWithoutCachesSpec.scala b/src/test/scala/com.snowplowanalytics.forex/ForexWithoutCachesSpec.scala
index d929de0..fd6cffe 100644
--- a/src/test/scala/com.snowplowanalytics.forex/ForexWithoutCachesSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/ForexWithoutCachesSpec.scala
@@ -15,6 +15,8 @@ package com.snowplowanalytics.forex
 import cats.effect.IO
 import org.specs2.mutable.Specification
 
+import model._
+
 /** Testing that setting cache size to zero will disable the use of cache */
 class ForexWithoutCachesSpec extends Specification {
   args(skipAll = sys.env.get("OER_KEY").isEmpty)
diff --git a/src/test/scala/com.snowplowanalytics.forex/oerclient/OerClientSpec.scala b/src/test/scala/com.snowplowanalytics.forex/OerClientSpec.scala
similarity index 99%
rename from src/test/scala/com.snowplowanalytics.forex/oerclient/OerClientSpec.scala
rename to src/test/scala/com.snowplowanalytics.forex/OerClientSpec.scala
index dc7c41d..a665ced 100644
--- a/src/test/scala/com.snowplowanalytics.forex/oerclient/OerClientSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/OerClientSpec.scala
@@ -11,7 +11,6 @@
  * See the Apache License Version 2.0 for the specific language governing permissions and limitations there under.
  */
 package com.snowplowanalytics.forex
-package oerclient
 
 import java.math.BigDecimal
 import java.time.ZonedDateTime
@@ -20,6 +19,8 @@ import cats.effect.IO
 import org.joda.money.CurrencyUnit
 import org.specs2.mutable.Specification
 
+import model._
+
 /** Testing methods for Open exchange rate client */
 class OerClientSpec extends Specification {
   args(skipAll = sys.env.get("OER_KEY").isEmpty)
diff --git a/src/test/scala/com.snowplowanalytics.forex/SpiedCacheSpec.scala b/src/test/scala/com.snowplowanalytics.forex/SpiedCacheSpec.scala
index 655ada0..29961b4 100644
--- a/src/test/scala/com.snowplowanalytics.forex/SpiedCacheSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/SpiedCacheSpec.scala
@@ -24,6 +24,7 @@ import org.specs2.mock.Mockito
 import org.specs2.mutable.Specification
 
 import com.snowplowanalytics.lrumap.CreateLruMap
+import model._
 
 /** Testing cache behaviours */
 class SpiedCacheSpec extends Specification with Mockito {
@@ -43,7 +44,12 @@ class SpiedCacheSpec extends Specification with Mockito {
       .create(config.eodCacheSize)
       .unsafeRunSync()
   )
-  val client = ForexClient.getClient[IO](config, Some(spiedNowishCache), Some(spiedEodCache))
+  val client = OerClient.getClient[IO](
+    config,
+    Some(spiedNowishCache),
+    Some(spiedEodCache),
+    Transport.httpTransport[IO]
+  )
 
   val spiedFx                = Forex[IO](config, client)
   val spiedFxWith5NowishSecs = Forex[IO](fxConfigWith5NowishSecs, client)
diff --git a/src/test/scala/com.snowplowanalytics.forex/UnsupportedEodSpec.scala b/src/test/scala/com.snowplowanalytics.forex/UnsupportedEodSpec.scala
index 0377fec..6fca724 100644
--- a/src/test/scala/com.snowplowanalytics.forex/UnsupportedEodSpec.scala
+++ b/src/test/scala/com.snowplowanalytics.forex/UnsupportedEodSpec.scala
@@ -18,7 +18,8 @@ import cats.effect.IO
 import org.joda.money.CurrencyUnit
 import org.specs2.mutable.Specification
 
-import oerclient.{OerResponseError, ResourcesNotAvailable}
+import errors._
+import model._
 
 /**
  *  Testing for exceptions caused by invalid dates