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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7637fe37e49794448ad1920eb53847016910c93369d3aa5a4faafc3cb95f10bf' 
  AND token = '87RMnxva5osRv1Hten/JaywqoPECQnTVdNGlDsXRXlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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