SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50891b6f0c5659762ad486baf3d80cf732689708b5fd0b1a0e90d4e6c2ca8d50' 
  AND token = 'MmncqcGXw1ZIzSP5UXyEkHUQJTSbEMa67U0/ONHYiKI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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