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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8ef14231e8da966cecc3f7f1780818430b0ead68d764a2cccdcad46c7d3ff21' 
  AND token = '8IJK9FHhwxiiar2cy4FweMmz3+da1E0/aIwZnJT0vp4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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