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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84e2123f30a1daf8392e6e13c00521afba50b2f268325d1c9e0ea0a84242d7a7' 
  AND token = '086JoLvjmOKuDBgTLtcvwxICzMNWKH2D5sU6nmLQy1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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