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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21ac66d7f7b49aaf2f1681bac46021a0c39fb75e2457b57e49b5327290059da' 
  AND token = 'pxfa/UljWARoQycvNLssNYX99K+ndu/k9c0zQnc//jM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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