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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50dc947f7abe6d5b92c01559942034562ecd1b8d2f917fa99ed83584941c0de4' 
  AND token = 'p5nLLWwWre3AqYL9BvbRgI1wXPd8Ix7uYeXlnX1PxyQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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