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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '16b1dc51d2f97ce4e4751dd73acdd7b8a186634cfc24d8661a8d0a49d8fc326e' 
  AND token = '6lR13RLYmT7AXVvTOWaV0JxwjSEWbnUjmdqmWoBcQ3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}