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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5fe84ca83c3da072b1bcd2e96cab08be092ff59f38a0ed7678d0fc8b350187a' 
  AND token = 'iiTG00Keg8EeXw+SbYlAwFBV+p5FYwVVM/ycx1FQAL4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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