SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cdd81f50ec9f248552b1650fd541b09db065ba8c98f1c52ca3100724ae7d927c' 
  AND token = '4ST6G3TzlzxiGzyff9TCKsrhsBL0caHK/PuHZytPRt4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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