SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd208b81a7f5ea8a144aad2421feb7ee7a5930458538666eae0cf95a86b587e93' 
  AND token = 'uZyu/mfUIWICFok/VrnqndRdbyTraf4mD4MTdtgAUSE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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