SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71e5240f61ca536b2d052d50131ac889dd2de3cbd748c12434afee6847529a54' 
  AND token = '+IYHz3LVVhyd7llKoUPgNY/lasH5Il36YwxLveQhpBE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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