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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8fe3200e3871be99631276520d8733ca19b9212d9dcd7f314d712199343c15e1' 
  AND token = '7QDhPrDGWV32eXf9isJ1nFhJ2TFatJtwtnnvWBMP/8U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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