SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe0879f8bae75aa134bca18e63fe1df6b0687057730b4e660f947f68c2420ac9' 
  AND token = 'aiiSsI3PC2z0lNX0YBKfCBfLRbxbXHhyLRI6m3D2UGM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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