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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a90fac5b4e51fbd95e6d2213b3d2d1e50601813a64a5acbee967088a219236d' 
  AND token = '5CF6w0uHJqzqfaDc6xxLrg+rdqTQjRZch2tL//nEPwg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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