SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39d981c34adb992eb97f7947c1bbb3b034ac6c58f3c530cf50f311a225d11728' 
  AND token = '2lLHjqfNwB2cuUBASjUuSNWqrBcHMi4iXmtFwjMJ7+k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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