SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0b520503c5e789583d15794f2d137fe48259116a235c47ddc88fd7b63796a718' 
  AND token = 'RszWqzhtZd7q4X2R66HVKqUOKRZktIHyoXOgUtj82rg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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