SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ffaf64e75f5936ff95ff348040e0960106933bf08afa6ff23d4c6a5d9381f6f' 
  AND token = 'QD6lyEuNmP2dOPwctj4mJZaIGCzBe8N+oPvys9uPefM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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