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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81b0ee15c4d8fe7f1a84683555d3ddca71d97a8b9568dbf30624551dec51f035' 
  AND token = 'A8pjRpnP4DNZzgdMefbqH6uq8m/ptTh6S296pMDt1r0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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