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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '351fc6a31ff29a0ae8d11f747c7f1b59bba74b09a5e1b1c5680d653e0d828bdd' 
  AND token = '4BDcZ4QfVaUMbWhwpFRMaqlIHPbMlOGQLFLdTQIf2ac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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