SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52dfa667de57f5d7f64d1584c078e14e39683365183349b7b480e66ce8f41f20' 
  AND token = 'nJDSP+zU99ONGdTu+8xouLBGUFmmzj+rrMmaUpxJhII=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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