SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5ce6fabd638dba08864e48326e3ebb6042124bc816c088603695871d8be43a82' 
  AND token = 'RvyKbaUp+cbRq3TMknVLVxB2oggvS0vSSzKeZmytcdk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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