SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29301551f0348035df03d668760c8094ac5ecf85d2748f138c1bb75477de2a3d' 
  AND token = 'JdB1tpbT+D7pER3ScA3GczVA0Uz5ZjSE+hGdC/MPVYg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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