SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71c5c7359474449762b79c8dbfd2e1321b9e3258dbb5579dbfa567a1712092b7' 
  AND token = 'VwLNs5ApvAbvyjSuBDVVf+slTjmMF1uY05lrz/ZGOj8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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