SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55b50dc584c11831dda587bf01b012cd68be0db8454829976ab22133005a5ea1' 
  AND token = 'RZOY4XifWU/eUl2+hjSrCkgvBL3TBUTgPUQwove/+rk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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