SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4ceff6e8c4ba17dbc5c6d3d990687e47c72a1dfa1a2c0c00a7cf7789120fb903' 
  AND token = 'ZiT2rU9KLtPCUvm8pQhjqRNK0GoVmu7izxmMHRv55pg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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