SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '391d336ad71ae60fb66e8943dd566f74a5cd7e37226231085c1aac4409381989' 
  AND token = '6K+CXvPJ/TKMwHOb2bM3kzAo/G6EWACNv3+BOjMlrFA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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