SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'be0c3e50072d6698dbc5b864386de40026d0a7e1385e3995d9f50e14743a9b68' 
  AND token = 'GDN6k0wtGXhVfOPZE/WRRAv+37BsY1Yrj4TK28qP1+Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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