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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c3b78c1eacc1876a62b8f20602753fa70e831461e7819da161385a9bc9e0f8b' 
  AND token = 'x/4d6ZS9j9ugdjbWN0Rhl+Z+dOSlJQ+GjggXz3EmXjc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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