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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3e7c14723d17b1ce193463308fb59fca6d40955d33ce2eab816ac5167bc2291' 
  AND token = 'MH6b7QgtfYt5Q9o/fGYPTDhl3lsIrpDLEaSpVCxd/qA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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