SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83236b28ff299da10a438b5355d3e2a8297de780dbd6382ece7620a33d436358' 
  AND token = 'uUZKy3L3y28iy/B6ACydcIKndIou3dKoIT69KckVolU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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