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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4fb5f7c4263b682fa10e93a45533e8a575eae2a2fb2944efa3cb73f9ca715d3' 
  AND token = 'px/U8/42c7FeB3FU0dE96rr5BIDI4yscVYklLn43bEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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