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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4476e21ac5b250441fab4ff37ab4b3bd4ea918d805fae0a4c414c6a7ef7ed648' 
  AND token = 'dRMEDWj1DY6EvhL8aKRXk8bw8cSSAZOOjQ8Jm/qipLQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}