SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '838e37ff146c1e1578e2a02c37a4e292c5a7dc8e38846dfa282dead91b2d4978' 
  AND token = '6+V7wDPvl+4Pp3xDknTG2IzWBgYxZfkSKRaFPKgfQXQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00048

JSON explain

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