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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c3c642b5c5dbd4ba98537787afdd3fcfcb5e3e5d968c752ab7a00e2f98adfc9' 
  AND token = 'juHFLqvgTtvN7i+gYemrCW+L3ynTcUvyv/2kuvqwT1U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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