SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51239438379c576e09c9372670d02ca516f103f5e4f93bdae796520fa99d66c3' 
  AND token = 'vn52SXOSuDKpu66hXwwBeB9vg5WBeoUxv02T1ZDrti4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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