SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '820feeb9974b34a9095461685df20d05cc983183fda2cc8404384ac165625b0c' 
  AND token = 'gnNeyB2UtgTJ3ofDCkXaywjMTmDuPK7F21VvNMUKdsU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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