SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9252a4380936d1844d773380cf7cfd8afbe0bf15d97b517d58518265a39acfcc' 
  AND token = 'r8szmbuaXXiT8ExqFPkLxQaeuTixTj/3fHPxi2wi0u0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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