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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8ee994dbf7dd20c0ab1dd60f29352f4f21c2750a5e1b30d90227c25dced428f' 
  AND token = 'rLm+ZjgMcZWG0eaJcg5ebQHk1Vr0n3/q2sZ7SK9cJRY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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