SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b6c400b35d2801f2e0a041339a03a957786e5723f236427e0864302fa794885' 
  AND token = 'X0j4JiWc89u+Vc/03PZ1UGsjNEFTIXkJgoSAVq9Y6gM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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