SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb799c9f3c84966d32c3e76fa4824f51de535a7e4840dafb9a5784da28645235' 
  AND token = 'Ppn1ErBrVR2DQ4KuQ5Z431SYFBiUyWgCdbEvVTo/4wY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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