SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '793dc93e02f7d6816e62e940689a8e622ebf54ead82939dea5fbf3b3b55efb7d' 
  AND token = 'itRHDmMFSNUPHSctfmzC21oT2+shauWQxCkIDPsavgw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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