SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6ebe735709cb6939712bb18e551a59d73b4bdcfa1b706f4b7050aa5a2185942' 
  AND token = 'XKmZGFGNEuOS9U4oSiCIAocPzKLXfoar26vCyM3C7Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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