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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff8bed2ce0ad07c0df1de5ac6d3a868f7b9e078cb4adf7da48e727777e81bfa8' 
  AND token = 'b2HMMTC6LsDdP7yGAsI4zZf8THwPerdHjz9GQwUya/Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00008

JSON explain

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