SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4e8c1fc62ea39c9962c007685086f6b2b97c271f755d4436016da617fbe8d87' 
  AND token = 'vwVoRyKAnhVjHRkM3mHkE2jOlzKYy+xgXWKhy6JJ8X8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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