SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39987336649ae2be8b4d451cafb93cce6d8edd3352ffa7a1c1b5aeed31de50ec' 
  AND token = 'i6luvfC6Sp0ifP9/vEPU7f7Yn0M/b7ECWPtBUrrzauE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00078

JSON explain

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