SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ccb876c86ebcdba192de10ea507c7e217061e2ab64c1faccb15eddbe53da622' 
  AND token = 'x4QUzSdzPsM4LWw1S7EaBv+xULusBVM0A7uh8dGklMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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