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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b608e9d0427dfa347a4cf71fd3b303dffb7995a3ad9c9c01d504dd4d3ad92b42' 
  AND token = 'jcluJ4R4ebDqiTxnH8EGNR5t4dYONvl+ZV70fTIi1K4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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