SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c93d2b8a837404b818010186f05887e262509510dfabd2eaeefd972ff5d1306' 
  AND token = 'POMskYTIvH/Dg4tae+IukMhT8Y9fd3CiqUlBVlqAfgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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