SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dd515a715f1549f50f4fa606dca2459993a41588d52646684dec8a3a5af94511' 
  AND token = 'iKbITmimHkd1csEOIpTN9wHwTpAG1S1ldppLHVDpirM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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