SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '504e360bfb99f3162488fe713c7bee74e7cfc9516b91cc00c2a858e1bd47a7be' 
  AND token = '6lwAHOURPofGa+BBguqEf4mjxNxCc0gljx85ujwzen0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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