SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '826a9f4a5f97957177e6d15b47f0daa2a3f3c488aebfbaa68a635dfcee761019' 
  AND token = '21xtdLxvXc+fsNXxIvDhTKTZpAaLzlqmtgcrs//aAuw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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