SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a40f2a3279d80c614a9c06804728c855823886b1502e020043b421a9841dc61' 
  AND token = 'DjASyOQIOq6HntqgCmUyVTpO/+gkDap8K0kDqHpq8x0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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