SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd96416a0335f393fba9629df65da37e749ead5a78738ff0e77ce33c64749d1da' 
  AND token = 'DXFYGlcVt9iJHdziSbXCjncIFfNEskbO2luONzdtcq0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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