SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c1c2d3fda7fda62f688cc57a821706454e616f179408016bb0d11ae61e643f8' 
  AND token = 'gk5YQhYnDkyYIA8hSClWatNu+2ry2WHQIRiHqyrrAsI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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