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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6fdd5f9077cefbaa02b2e5f28952dbd9137bff70bb4b7d414aa975c8d53f91c' 
  AND token = 'FmZ5VT2afBPma4INa4kYrFr+MNrQ+VjCXNrm4G8dBEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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