SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '791bf9cb81805e26cfe30f1fee987819c07467374d514f7d5a6574c666c0e38c' 
  AND token = 'xStyz3NSka+Azwr1WFdlR/yfa4DTriDKBwsxEJhNVz0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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