SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b12355d05c2d1701e98098b59718d23877e28906660f34fc718e241e97ff6580' 
  AND token = 'BZObf0ul+3TdenfJbEmVhC2TWH4E/Qsyd7DHORJqTTo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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