SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b286ffddd0c075038bfb71804759da2345e906d26f3be9da013b26bc27c869f7' 
  AND token = '0oFGvnViSGU2o1BmYl2A5dH9bOg209ElN7TcJVJVgJA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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