SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b6e8f70c170984218c6df51c324a3129ccf35050d0f23acf4eb23ca26fd509c4' 
  AND token = 'Ds6uFWGDj1VamYCyq/9KXmAw3XBY1ljnQS6NaRoulVg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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