SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55fcc4b93f98108409815e168cf654896b15a1b11a2951edc0a10ba80c64e961' 
  AND token = 'u/edZIo+/ilQJECRrgbTh9pgPJ3ume/jLsMAo1PvWec=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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