SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a54bf5c8ffa3ed2969759fa3a5110247aca60b4f0c1be91f1cbb392e027ba877' 
  AND token = 'Qz6lpffKbSiChHFN5uW+bBvgcillPqdSGKQ+DjkxqNQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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