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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4c141735e0a4de268796a5302755c3b2a0fe241e4dd10f47911daca3248747a4' 
  AND token = '3RaUCWJsvk8UiXr5wN5IjhIs67HxbUi60UTO48mdQxM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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