SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5476ce7c7660300ab277c0cb0b649d1d1686981c6230de476f819ca21c1aeda' 
  AND token = 'QIdswuXKwIoHvsOvUvtaGQUVdIkTSu+DaLHFmbVBU/o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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