SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '394fa703254fa2c8a9b6c62af797f6a50c3bf9f273aba30a221c5bffd288b10f' 
  AND token = 'RYxUd6pklZaNj3vWRDsys+mA/LIreBn6DuWIxQHv9+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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