SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c66c7300601edaed0c02be31e551e314d9e3c39fcdf6f4ea550e2e0a65bda08' 
  AND token = 'F+sMug8YBDZjeMvDrotDqYTAJXxE94ZjBPIqAQNGaYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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