SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b0f35e16d3ccc052922dd7598f74b44bf1e709a399916917a1bb04f22886412' 
  AND token = 'rmccHWaXZlLViDGRRo4gqS6mH1EWvTLgMli2s3Nwt+A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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