SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9f0477d03866c1840e6eb874193527e5450fed6f17133637a51c7e552804d83c' 
  AND token = 'gb/1vGcKrZ0PAnd3xAuBy9az0+DhxwFSWHlypxHEQUA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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