SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8f926a31d32456640222d35f758d4f299676fa8adabf8af73977fb9a5587bf8' 
  AND token = 'zQoM6h+kZGcDuA3BOfVVJxVLpGptxUKlzoJKRvecDFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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