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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83c93557341af92ffedbeba95eb1385834c8ee71b3be46039d9b4f7596ab5251' 
  AND token = '6NqsiJH3qsgqq8tpxgU3FScTOcZze7axwnlwNs792eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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