SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '784cb16bcba0eda14c9e260a45276103fd775255d194bd3975de0ba2bd507ae7' 
  AND token = 'yE3YUAebLV4+IU06ILgB74+j0g3AlJZvhWuBAxS2CMs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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