SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b53da63794881e5841b502a782cab740c877c42de6a4acb9188d6cf5855eb311' 
  AND token = 'WMk6bOTIC1n7yqwPyF/faul2TLDBu9iRClXG+IhT/xw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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