SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6801ca35f5588bf70a6fcadef782466cb845bf2758c57b7cc1078e452c8b716' 
  AND token = '6ExUltIaKc9cMPktSyr5EFVarHZFLlDZbHekGl/R55g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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