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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f719383c78bcab92f754a3f8e9d0944ff7da445eb8fa3473c8c30ad2d0a8f21' 
  AND token = '89OOtgYeRiTalYTj8rbPxgMSo+/Mj6DGXHwoJ9Xpp0s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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