SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4975d5cc6aa533c96687c468b1f94634740120e08b927730e304d373e91368eb' 
  AND token = '0Jv4paNYEpBfvhqmGzvffATNS+bnD6fz3aApn8FwXLA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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