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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ed1019e55485058b368147e07c3b3de333f9f0e17e3d4cec1986144c9b5bf9f3' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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