SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '729321b65db2689942cb8569c0707b42dc64b5ec03d4c3f0db4edee6e026479a' 
  AND token = 'thy1OhZlg1Np8IMLTIptfAgSHEw6Js0b4zEnakg1uPo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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