SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '304b616a1d55e2265b120841eb9998fc298b0571a195acb4f2402a8cc2663386' 
  AND token = 'k+f3nbF7v7pMjPTGVpva21u8r72F+ti/a8UrVSoRlbI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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