SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd18bf7e4868f054875b30777fbe0acace720e7dccf2a11a689b0402a2da78d49' 
  AND token = 'BM8JOSGkPuK645ox4ku9NH8RSAll+kpdJHcZHy/TD1k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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