SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8536826d6860339c865f05922c40f896a40d85f8f3d85f25b49a6b187d80961' 
  AND token = 'obcSiJ75rVyCP+TyndpMPCZvAjCEmGRTTH+U9nY3CWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}