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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'b6a3fce4509eef2b188a857947d9c94e2c1aec7b1d8da454d5518ded8ead0241' 
  AND token = 'mrjQ7eu8zJfnGE/+XXnzRIX9Hv4n9lu/W4rMjsR5dXc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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