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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '66249e2f82a84ee0cfb63eb0381e8fca483bb0dcbdf651504e33249684aa691f' 
  AND token = '6x0QDJ/adnRdoyVqLIN5ARZeQkIYzb4hkn+Hffh5BC4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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