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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eb8f9ed014e22d3f75bdadc8e43d76b1c4a98728e950a5f22518285fb749276a' 
  AND token = 'R/KJMCI3+DatBx02OnSsj5OF60DFzOE2U2RDlOk/XKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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