SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a559a9c694adc25a388e9e47c0b6fa5a35207209f8ef37ffe03b2267894e7f' 
  AND token = 'EXyRx72ppmlQegMnzdICj6+GribtLUBbv3HzWS+jvtE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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