SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f15f17ad9ab867155c78b88a8ed9d1768b158a5866545352d484cb75ff569f45' 
  AND token = 'mtFmgp1HpRY5TadWIRRKLnVtnTRfyYewFPWT4RRMi5w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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