SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c8ac348f317edbfe3ac2f4f8494dad0352018f26b72d25f51a363fe0a0a2646' 
  AND token = 'G9zQUTlRGdeYQswRvrST6ZE/SbyD0QhngJitbAftkpY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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