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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac976f7cb4e16d6fe460682012a44dcdaa03cf683e615454a481bca1817f6c1d' 
  AND token = 'xka9s9Mplz+HZVHu6yGjN6VpsH+Z48OxQ/+uzs/kvKQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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