SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2c8f24a41cebfb9b70656ec97f86ce7822963b84f9518e6ca4f76db37a4bb043' 
  AND token = 'ZpiObkbBImUYBR1igiohL8+0YAGnrp409Ot70sLz6yQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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