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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5e3546fccd05a9c82889861f31637e6a6a8d1f4017f64c63f10d54a2c5defb8' 
  AND token = 'cVk2iXV1eM1PFqcYBQpIR9+EOfvb+M7hdoQWVx6REU4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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