SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a6de4fc2b3275069089ef0206a67638aae8242c7fadd12333b57bf6997dfd07d' 
  AND token = 'osRHsM7onal5JL4wocG2AxlsFqP1PkUBP0EHB7EpIm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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