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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6b22bfb5a1700b1d7d0e48f6e9558951f483fc7f40ec89054902c334fdc0b2f' 
  AND token = '879El4ubrUSMVyte5uF5nbPcKyC0FrEPqrDibPHeDac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}