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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fbc3e8b03ec3e27b75e5cfcb8212be86b37b268702ca20865422d01b635b9890' 
  AND token = 'f7ZdbcFGIQ0yiyNXuFjt+XmjDwhLaiEKE9hyMNq99Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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