SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e312ee1bb1499242ffe3e2dde6b1371192d0325344052367c6706a3656add40' 
  AND token = 'EXgWzASFSmvvDx09WiNOqJ7YZ7wnjRgj1pUWB+pHY9k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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