SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b8b89886c0f0be4e7c454ee76ba703d3c2ed6b64210d8564a832bc71c76a144' 
  AND token = '7QMSo+ojg4jqliKLY59fpVv3tBevB7FvZqXHOHFUg2E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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