SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '356281472726a96e9dfa9c032e835f308d6228b68e6234314117fbdd4c51a6c4' 
  AND token = '3OQO+T0LmhcijZRf054fjQfyJdvZAHBPFyvkPvrY/vg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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