SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ab3e649f84400fa140f469e74a51b8a03f6660a6d84f20168b3955c68cd85cf' 
  AND token = '6kRoKewqdA3NfjMsmCWavs4KZLEbmaRIebbungEMYRk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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