SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '740cd8635981bfd3bd0a2f0fe59cb3d5e5eae98e136eb6b6aabf82743999d3bd' 
  AND token = 'k8qC9li7rRbJ/bbfjJEEl3IY1MfA7oR/YlkRFQVDrjY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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