SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cc3e03e67917bdb58562da458be662e39c1a3960f22e09c84e1c535ecddb3550' 
  AND token = 'IslUyZq0ceV+QKk1w0jC/TsV8Xve4iURMLJvriSy/pE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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