SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5a7c50b0f2c4878cd12bf042c318f9546f85d71a04e161f99d136962aba738f0' 
  AND token = '0O4yi3EhfwWVCfTPzjxWlLqVmuJjtriVWIMJDpUVfXs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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