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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75684d6b0d9f69b5fcf0d1b5f6e9f50b752c56dae02c30543083a44672ab5c72' 
  AND token = '6OC10TvBp+OqrLXlDAj57AoFyZx5bR6K0+F2tuBiKTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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