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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3999fd45ca8bf0806292140c0da6f05e4ab102c71018f2f4877e61371e8a5ce' 
  AND token = 'rZe8NQ0yDXW+AvoTdzFo4aX5uyhBpmXWfREYVqIPvHE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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