SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3904c266e1666678559a17a72c111537df759880f984dbb13ef1d5b51a913e7' 
  AND token = 'QrrPy7BFXDza5ZgeGRNn2A0PsO5HYv+bqh8v0oFzQQI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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