SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5691e053cde9eb301aea59aff23e9405d41960e53b43f7ec77aef3426cca3cd4' 
  AND token = 'RCg6AAE5sacDjPdN27ExZUTTi8drCbngFAyhEVGyIKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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