SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'aff7e934aa7d493bb1126351c9efe463d71ec0ae37574d607485e90984829880' 
  AND token = 'UkRtFhk4au8fdbXJgtCRTwLhRAM5j3ocQpIcQkD+ao0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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