SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '429c8c40136661bfd540c036bcaa86355be209f32a21eaf910184a0a2da9db46' 
  AND token = 'cPWn9tOz4gWmmHVEub/bjKF29JHafzrNP8aNgEuZank=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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