SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '63b31910b28e70a571748d11e59db86385b4338967b2f8357199d25705a0def8' 
  AND token = 'CtAgLBI/BApSH6pX8edvVfaHXkUWGwPnNlIFa2jDkUg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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