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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e6e3509e4a96179db818b1deb54ed3dbb200ce034ef9039b264cf869e9165c' 
  AND token = '3AGKYy/CWETknR5znyTVKLxHG7nlgKpoQUaJqzlPSl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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