SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8e4982fe3f4fdd8319afb88faee5df8345849fcf493b462385ff1991bb8ee678' 
  AND token = 'D47V1kUG32YBEeQWL1sP0GBkoe0KxmpRafE4zbswkyI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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