SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '90d91195355452ee1e7a75afc29cb948f5002a3adc41b93d5798fd7913351334' 
  AND token = '15sN57km4YIqWRdWJoSOHzBZc50zOQ1Ly2Gj7tOWUwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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