SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12d6db267bf0fa4d74c31559adea8d6af411bd0ab6c08c5ca926076b020c1b2f' 
  AND token = 'ieQws9pBqVhSSpGgWYo555QONTsHLVyw8sF+8JexRGU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}