SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '990f6a90496c2ee3278937ff7cbb7a8fb6f5e50d4f33aac9e324c08b160714d1' 
  AND token = 'btl3FdtPRhpj2DgHVLC5TgD+UCJWH/pmJ1qhIdBKezE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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