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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6df5ef02efb1600ea096103ce53211a8670efd7079980b094ada00920daa995' 
  AND token = 'VjR17RvE4mYi+Sz+Z/AD9fpUdXBnbUzxASEJx78vEe0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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