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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe29cce34ee97cc0f302b3e059b1f942d58a2bebee25ed14b9dede5edddf41bb' 
  AND token = 'mdFdJ7xRPVJmM3DuRT5VkuM4DqPUA+qBT+Iec1xhSnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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