SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f021bedfd321d39fd0a3c400532d89d14f015ec21fb957666f8ffe73c23109e' 
  AND token = 'UWvSnEXncO2XfVJvbGOSadrvcSrftbEnkdcMm34S58M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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