SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b50c3365deeb490ab4dc3a478e4a1f537c7643967a03b3277d9886b017f039e2' 
  AND token = 'LjD51U5L9tRXaHwPzjfz2VLJDSVbUY6lh/8QhI2Rems=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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