diff --git a/src/common/config/env.validation.ts b/src/common/config/env.validation.ts
index b3eb83cc..80efc416 100644
--- a/src/common/config/env.validation.ts
+++ b/src/common/config/env.validation.ts
@@ -6,213 +6,230 @@ import {
   IsEnum,
   IsInt,
   IsNotEmpty,
-  IsNumber,
   IsObject,
+  IsOptional,
   IsPort,
+  IsPositive,
   IsString,
+  IsUrl,
   Max,
   Min,
-  MinLength,
   ValidateIf,
   validateSync,
 } from 'class-validator';
 
-import { Environment, LogFormat, LogLevel } from './interfaces';
-
-export enum Network {
-  Mainnet = 1,
-  Goerli = 5,
-  Holesky = 17000,
-  Kintsugi = 1337702,
-}
-
-export enum ValidatorRegistrySource {
-  Lido = 'lido',
-  File = 'file',
-  KeysAPI = 'keysapi',
-}
-
-export enum WorkingMode {
-  Finalized = 'finalized',
-  Head = 'head',
-}
-
-const toBoolean = (value: any): boolean => {
-  if (typeof value === 'boolean') {
-    return value;
-  }
-
-  if (typeof value === 'number') {
-    return !!value;
-  }
-
-  if (!(typeof value === 'string')) {
-    return false;
-  }
-
-  switch (value.toLowerCase().trim()) {
-    case 'true':
-    case 'yes':
-    case '1':
-      return true;
-    case 'false':
-    case 'no':
-    case '0':
-    case null:
-      return false;
-    default:
-      return false;
-  }
-};
+import { Environment, LogFormat, LogLevel, Network, ValidatorRegistrySource, WorkingMode } from './interfaces';
 
 export class EnvironmentVariables {
+  @IsOptional()
   @IsEnum(Environment)
-  NODE_ENV: Environment = Environment.development;
+  @Transform(({ value }) => value || Environment.development)
+  public NODE_ENV: Environment = Environment.development;
 
-  @IsNumber()
-  @Min(1025)
-  @Max(65535)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
-  public HTTP_PORT = 8080;
+  @IsOptional()
+  @IsPort()
+  @Transform(({ value }) => value || '8080')
+  public HTTP_PORT = '8080';
 
+  @IsOptional()
   @IsEnum(LogLevel)
-  LOG_LEVEL: LogLevel = LogLevel.info;
+  @Transform(({ value }) => value || LogLevel.info)
+  public LOG_LEVEL: LogLevel = LogLevel.info;
 
+  @IsOptional()
   @IsEnum(LogFormat)
-  LOG_FORMAT: LogFormat = LogFormat.json;
+  @Transform(({ value }) => value || LogFormat.json)
+  public LOG_FORMAT: LogFormat = LogFormat.json;
 
+  @IsOptional()
   @IsBoolean()
-  @Transform(({ value }) => toBoolean(value), { toClassOnly: true })
+  @Transform(toBoolean({ defaultValue: false }))
   public DRY_RUN = false;
 
+  @ValidateIf((vars) => vars.NODE_ENV !== Environment.test)
   @IsNotEmpty()
   @IsString()
-  @MinLength(2)
-  @ValidateIf((vars) => vars.NODE_ENV != Environment.test)
   public DB_HOST!: string;
 
+  @ValidateIf((vars) => vars.NODE_ENV !== Environment.test)
+  @IsNotEmpty()
   @IsString()
-  @MinLength(3)
-  @ValidateIf((vars) => vars.NODE_ENV != Environment.test)
   public DB_USER!: string;
 
+  @ValidateIf((vars) => vars.NODE_ENV !== Environment.test)
+  @IsOptional()
   @IsString()
-  @MinLength(0)
-  @ValidateIf((vars) => vars.NODE_ENV != Environment.test)
-  public DB_PASSWORD!: string;
+  public DB_PASSWORD = '';
 
+  @ValidateIf((vars) => vars.NODE_ENV !== Environment.test)
   @IsNotEmpty()
-  @MinLength(1)
-  @ValidateIf((vars) => vars.NODE_ENV != Environment.test)
+  @IsString()
   public DB_NAME!: string;
 
+  @IsOptional()
   @IsPort()
+  @Transform(({ value }) => value || '8123')
   public DB_PORT = '8123';
 
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 10 }))
   public DB_MAX_RETRIES = 10;
 
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 1 }))
   public DB_MIN_BACKOFF_SEC = 1;
 
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 120 }))
   public DB_MAX_BACKOFF_SEC = 120;
 
+  @ValidateIf((vars) => vars.NODE_ENV !== Environment.test)
   @IsNotEmpty()
-  @IsInt()
-  @Min(1)
-  @Max(5000000)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
-  @ValidateIf((vars) => vars.VALIDATOR_REGISTRY_SOURCE == ValidatorRegistrySource.Lido && vars.NODE_ENV != Environment.test)
+  @IsEnum(Network)
+  @Transform(({ value }) => parseInt(value, 10))
   public ETH_NETWORK!: Network;
 
+  @ValidateIf((vars) => vars.VALIDATOR_REGISTRY_SOURCE === ValidatorRegistrySource.Lido && vars.NODE_ENV !== Environment.test)
+  @IsNotEmpty()
   @IsArray()
   @ArrayMinSize(1)
-  @Transform(({ value }) => value.split(','))
-  @ValidateIf((vars) => vars.VALIDATOR_REGISTRY_SOURCE == ValidatorRegistrySource.Lido && vars.NODE_ENV != Environment.test)
+  @IsUrl(
+    {
+      require_protocol: true,
+    },
+    {
+      each: true,
+    },
+  )
+  @Transform(({ value }) => toArrayOfUrls(value))
   public EL_RPC_URLS: string[] = [];
 
+  @ValidateIf((vars) => vars.NODE_ENV !== Environment.test)
+  @IsNotEmpty()
   @IsArray()
   @ArrayMinSize(1)
-  @Transform(({ value }) => value.split(','))
-  @ValidateIf((vars) => vars.NODE_ENV != Environment.test)
-  public CL_API_URLS!: string[];
-
+  @IsUrl(
+    {
+      require_protocol: true,
+    },
+    {
+      each: true,
+    },
+  )
+  @Transform(({ value }) => toArrayOfUrls(value))
+  public CL_API_URLS: string[] = [];
+
+  @IsOptional()
   @IsInt()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 500 }))
   public CL_API_RETRY_DELAY_MS = 500;
 
-  @IsNumber()
+  @IsOptional()
+  @IsInt()
   @Min(5000)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @Transform(toNumber({ defaultValue: 15000 }))
   public CL_API_GET_RESPONSE_TIMEOUT = 15000;
 
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 1 }))
   public CL_API_MAX_RETRIES = 1;
 
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 1 }))
   public CL_API_GET_BLOCK_INFO_MAX_RETRIES = 1;
 
-  @IsNumber()
-  @Min(74240) // Altair
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
   @ValidateIf((vars) => vars.ETH_NETWORK === Network.Mainnet)
+  @IsOptional()
+  @IsInt()
+  @Min(74240) // Altair
+  @Transform(toNumber({ defaultValue: 155000 }))
   public START_EPOCH = 155000;
 
-  @IsNumber()
+  @IsOptional()
+  @IsInt()
   @Min(32)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @Transform(toNumber({ defaultValue: 32 }))
   public FETCH_INTERVAL_SLOTS = 32;
 
+  @IsOptional()
   @IsInt()
-  @Min(1)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 12 }))
   public CHAIN_SLOT_TIME_SECONDS = 12;
 
+  @IsOptional()
   @IsEnum(ValidatorRegistrySource)
+  @Transform(({ value }) => value || ValidatorRegistrySource.Lido)
   public VALIDATOR_REGISTRY_SOURCE: ValidatorRegistrySource = ValidatorRegistrySource.Lido;
 
+  @IsOptional()
   @IsString()
+  @Transform(({ value }) => value || './docker/validators/custom_mainnet.yaml')
   public VALIDATOR_REGISTRY_FILE_SOURCE_PATH = './docker/validators/custom_mainnet.yaml';
 
+  @IsOptional()
   @IsString()
+  @Transform(({ value }) => value || './docker/validators/lido_mainnet.db')
   public VALIDATOR_REGISTRY_LIDO_SOURCE_SQLITE_CACHE_PATH = './docker/validators/lido_mainnet.db';
 
+  @ValidateIf((vars) => vars.VALIDATOR_REGISTRY_SOURCE === ValidatorRegistrySource.KeysAPI && vars.NODE_ENV !== Environment.test)
+  @IsNotEmpty()
   @IsArray()
   @ArrayMinSize(1)
-  @Transform(({ value }) => value.split(','))
-  @ValidateIf((vars) => vars.VALIDATOR_REGISTRY_SOURCE == ValidatorRegistrySource.KeysAPI && vars.NODE_ENV != Environment.test)
-  public VALIDATOR_REGISTRY_KEYSAPI_SOURCE_URLS!: string[];
-
+  @IsUrl(
+    {
+      require_protocol: true,
+    },
+    {
+      each: true,
+    },
+  )
+  @Transform(({ value }) => toArrayOfUrls(value))
+  public VALIDATOR_REGISTRY_KEYSAPI_SOURCE_URLS: string[] = [];
+
+  @IsOptional()
   @IsInt()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 500 }))
   public VALIDATOR_REGISTRY_KEYSAPI_SOURCE_RETRY_DELAY_MS = 500;
 
-  @IsNumber()
+  @IsOptional()
+  @IsInt()
   @Min(5000)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @Transform(toNumber({ defaultValue: 30000 }))
   public VALIDATOR_REGISTRY_KEYSAPI_SOURCE_RESPONSE_TIMEOUT = 30000;
 
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @Min(0)
+  @Transform(toNumber({ defaultValue: 2 }))
   public VALIDATOR_REGISTRY_KEYSAPI_SOURCE_MAX_RETRIES = 2;
 
   /**
    * Use a file with list of validators that are stuck and should be excluded from the monitoring metrics
    */
+  @IsOptional()
   @IsBoolean()
-  @Transform(({ value }) => toBoolean(value), { toClassOnly: true })
+  @Transform(toBoolean({ defaultValue: false }))
   public VALIDATOR_USE_STUCK_KEYS_FILE = false;
 
   /**
    * Path to file with list of validators that are stuck and should be excluded from the monitoring metrics
    */
+  @IsOptional()
   @IsString()
+  @Transform(({ value }) => value || './docker/validators/stuck_keys.yaml')
   public VALIDATOR_STUCK_KEYS_FILE_PATH = './docker/validators/stuck_keys.yaml';
 
   /**
@@ -225,10 +242,11 @@ export class EnvironmentVariables {
    *  Validator 1 participation is bad, because 78 < (99 - 10)
    *  Validator 2 participation is ok, because 98 > (99 - 10)
    */
-  @IsNumber()
+  @IsOptional()
+  @IsInt()
   @Min(0)
   @Max(100)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @Transform(toNumber({ defaultValue: 0 }))
   public SYNC_PARTICIPATION_DISTANCE_DOWN_FROM_CHAIN_AVG = 0;
 
   /**
@@ -238,10 +256,11 @@ export class EnvironmentVariables {
    *  SYNC_PARTICIPATION_EPOCHS_LESS_THAN_CHAIN_AVG = 3
    *  Then we alert about that
    */
-  @IsNumber()
-  @Min(1)
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
   @Max(10)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @Transform(toNumber({ defaultValue: 3 }))
   public SYNC_PARTICIPATION_EPOCHS_LESS_THAN_CHAIN_AVG = 3;
 
   /**
@@ -251,19 +270,23 @@ export class EnvironmentVariables {
    *  BAD_ATTESTATION_EPOCHS = 3
    *  Then we alert about that
    */
-  @IsNumber()
-  @Min(1)
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
   @Max(10)
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @Transform(toNumber({ defaultValue: 3 }))
   public BAD_ATTESTATION_EPOCHS = 3;
 
   /**
    * Critical alerts will be sent for NOs with validators count greater this value
    */
-  @IsNumber()
-  @Transform(({ value }) => parseInt(value, 10), { toClassOnly: true })
+  @IsOptional()
+  @IsInt()
+  @IsPositive()
+  @Transform(toNumber({ defaultValue: 100 }))
   public CRITICAL_ALERTS_MIN_VAL_COUNT = 100;
 
+  @IsOptional()
   @IsString()
   public CRITICAL_ALERTS_ALERTMANAGER_URL = '';
 
@@ -271,11 +294,14 @@ export class EnvironmentVariables {
    * Additional labels for critical alerts. Must be in JSON string format.
    * For example - '{"a":"valueA","b":"valueB"}'
    */
+  @IsOptional()
   @IsObject()
-  @Transform(({ value }) => JSON.parse(value), { toClassOnly: true })
+  @Transform(({ value }) => toObject(value))
   public CRITICAL_ALERTS_ALERTMANAGER_LABELS = {};
 
+  @IsOptional()
   @IsEnum(WorkingMode)
+  @Transform(({ value }) => value || WorkingMode.Finalized)
   public WORKING_MODE = WorkingMode.Finalized;
 }
 
@@ -292,3 +318,59 @@ export function validate(config: Record<string, unknown>) {
 
   return validatedConfig;
 }
+
+// ====================================================================================================================
+// PRIVATE FUNCTIONS
+// ====================================================================================================================
+function toNumber({ defaultValue }) {
+  return function ({ value }) {
+    if (value == null || value === '') {
+      return defaultValue;
+    }
+    return Number(value);
+  };
+}
+
+function toBoolean({ defaultValue }) {
+  return function ({ value }) {
+    if (value == null || value === '') {
+      return defaultValue;
+    }
+
+    if (typeof value === 'boolean') {
+      return value;
+    }
+
+    const str = value.toString().toLowerCase().trim();
+
+    if (str === 'true') {
+      return true;
+    }
+
+    if (str === 'false') {
+      return false;
+    }
+
+    return value;
+  };
+}
+
+function toArrayOfUrls(url: string | null): string[] {
+  if (url == null || url === '') {
+    return [];
+  }
+
+  return url.split(',').map((str) => str.trim().replace(/\/$/, ''));
+}
+
+function toObject(str: string | null): Object | string {
+  if (str == null || str === '') {
+    return {};
+  }
+
+  try {
+    return JSON.parse(str);
+  } catch (e) {
+    return str;
+  }
+}
diff --git a/src/common/config/interfaces/environment.interface.ts b/src/common/config/interfaces/environment.interface.ts
index 58dc31f1..96445a3e 100644
--- a/src/common/config/interfaces/environment.interface.ts
+++ b/src/common/config/interfaces/environment.interface.ts
@@ -18,3 +18,21 @@ export enum LogFormat {
   json = 'json',
   simple = 'simple',
 }
+
+export enum Network {
+  Mainnet = 1,
+  Goerli = 5,
+  Holesky = 17000,
+  Kintsugi = 1337702,
+}
+
+export enum ValidatorRegistrySource {
+  Lido = 'lido',
+  File = 'file',
+  KeysAPI = 'keysapi',
+}
+
+export enum WorkingMode {
+  Finalized = 'finalized',
+  Head = 'head',
+}