SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a75f3feb68e44cbda0057198985960cfe08ffc1ed8d11fc399da5a9f326c9fc7' 
  AND token = 'gkabj7ASz0DyA2ndOf5ASFfrid/QEouluhW2Egy2z6E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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