SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a252b401dabb44fcea90a836828ad85d7228bc89863894ee34b3c50977949c39' 
  AND token = 'HLfaFreF5b2cPo4eGN7bTYhnV36gawQ2jC1LDwn3i4A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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