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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5fcf858f0ec1671929d9428e816b40831c0b9e62a6bb8a38bac8e3895ffe1c6' 
  AND token = 'OE20jDLNptpZKPt2bTZMjNf2C64LFiM9aMUpmY+bXSk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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