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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e57b27a9b6583b3bd54a6fb3af60d17df76588bbe256247c2665893ed68497' 
  AND token = 'I7d2YNitcjsrC5kpEQO1Hei5QgjpDD/1f+4qGZCtRuI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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