SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd51bb365173547122da6dc633eb142bcdfc41b75accb2fa4b957d81692e6e8f3' 
  AND token = 'lDfibaJIoKsbanEWFWKquuzzZP/LFApf5HvloAZAsI4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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