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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2e5fe7e9b57ed4459a353eb4bfa76a84acdaf9d23f3f44e450ba737ebb9ca50' 
  AND token = 'sr/10i4pZktji1bPI+ZZ2quvf3ZphCYvAUuULbsG1us=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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