SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ab35912d591de66dea915f6de830bbd66fd152e82e7c9f9e7a1bc943529ca7e3' 
  AND token = '+aq0JAGPhgJ5inA/WvMTeE/CKIhnFjDesXCEgx/+Y4c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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