SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a940d0f00b2764c1b8ff43fedb79f8991ea4f44b97c61fde47b008ef67afcece' 
  AND token = 'rlvArMPDng4uiCx0EFhHwOKdgndJbgyrSz7JDL5A03I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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