SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31dc5dc5bab7e12450d182728238fea9ae99cee0fb6468738bf6b308cb43573a' 
  AND token = 'ZQikCpkewjHb0sTAL0IjsQj1oYMumHy9whPlE224MEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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