SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91321c42472f5ef717bb2f96e3099a2148a498bc6f40a383e524e10a5f1be733' 
  AND token = 'mhSSrJ4xC7R/ttWEJ+WY7vgUwix3QCFkavglXVcUouY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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