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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd38b5468ed19f5bd5b0eedc39bc1f6ff14bfd7c6552bbdf83a52fa9ec8ccca75' 
  AND token = 'ya8JuX7xXpVYFJfqf8j4kL2rNMGBqQBWS/zV92/ay/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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