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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21ef34b8928e315d5fd49079cd58e3eb05ae364719f9afe70b87dd342d5cc9a2' 
  AND token = '1jffzk3l70Nk8M9QokPzvT/djBvTytmS7VaAY0j3DuQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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