SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ca8eb55fd52479412918477622678629bb5b708adeb93be2578b15439ecbafd' 
  AND token = '5UfWbH4vrGVWRfOz2UWDUfk+kZoDdnckYqrdF9Ye6IA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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