SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '568439690a43683f7a71a81fc9b5d08b40ea47198037255fd7f2f75bdff40bf4' 
  AND token = 'ee9MXHAN+nfqOVOW9bqvufzMnxgNWQcnWmEWUE5dOlw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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