SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a5568c78eaed8700da7f0e9047a7edd27f6f501c4938a8e0873134bb9b41d354' 
  AND token = 'aSeLbWMHtPDieeRHquHDM+qhHA0boChZAWgtAoMc5OI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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