SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8782e2545d8a2434ed239df34fe430624698e579fd24992ade229ecca0d4495' 
  AND token = 'fx/r37SmosTvV3laOabBiU+hmrlDqN40AhVrG/3Agrs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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