SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a4d83fd939a600ab3b86c36311e3f2cc64778f50abf977168e7168abaa45759' 
  AND token = '35KwczXIdu/n7NgnZAvKxFDDrgzM+16+/NWt7RsvZzE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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