SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c138a6e134fb0a2668b44ccf9ea033dd0a74e8085d15af7cc80f50a91f3fd25c' 
  AND token = 'sb+lFKpjCmaGsB2oWda3lsplD3LevZPbwPAAAWvicsU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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