SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '89b82d6579ff314ccdf011cb8fabd7740421b274a450dbef8f9f95534e7c7c7c' 
  AND token = 'C+PsRq8lqkOVxWGs+CInTA6edZXWyHGEURMfVtt/OTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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