SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8640d9125485a2c5c5d9c28cd2a24367fe347c9e8dd5d6a90b61136b962bdd4' 
  AND token = 'EzABUQwZjiSYgPZOSFsSFm1pF/m4Dt9WQ1gtyTXPVdI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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