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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c36b12a7520fa5802756dd2a239785365cb04768e5e8957ba8fded0f24f6aa37' 
  AND token = 'ZayPDtMx4HgxiJulcfG7Z1KyXFDPgshCDR3vMKDKSTs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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