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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4f7c7d851fdbdbf768d64b8a31eb6abf05e8668fd6e840efa993b7d3b849a4a' 
  AND token = 'sum7YkoyNNwiBvZTuQtRlJp031izy7WLpy2uOlP9lhU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00049

JSON explain

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