SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f266171cafed642a0c3669ee73784c992f36d53bd9eef06b3c0821bee2fd18e9' 
  AND token = 'W6XYmMTXaHrdZRXObOnz64Z88v+RdJn1ncpwmTONyOQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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