SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68dec5c3b9b1e6a79d6f974d070dcada9d72ccb0246d9f21ac99bd1b4bf1a51e' 
  AND token = 'Qwlc+6pl7DiOpm3Qs9orpp+kjXurv0QnrG0HzaMpjEM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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