SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2c6c78d2218129caa1981f0c85b53bfdc7277f88f490d380337d9f17ad13ff04' 
  AND token = 'FM7isbrRkmiG6u8l2zNspUM6GkSwqR9z/tauiH7L2Fw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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